What Presidential Power Over Territories Actually Allows

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On January 7, 2026, President Donald Trump declared from Air Force One that the United States would act on Greenland “whether they like it or not.” The question is whether American constitutional law permits a president to acquire foreign territory through threats, purchase negotiations, or military action based solely on his assessment of national security needs.

It doesn’t.

No emergency provision, no national security doctrine, no executive power theory permits a president to act alone to expand U.S. territory. Whether through purchase (requiring Congress voting to spend money and Senate approval of treaties), military conquest (requiring a declaration of war), or diplomatic negotiation (requiring Senate approval of treaties), congressional action is mandatory. The Constitution gives Congress the power to control treaties, territory, foreign commerce, and declarations of war. Presidents can’t invoke “national security” and bypass these requirements.

The ways to stop presidents from grabbing too much power aren’t constitutional principles alone. They’re specific procedures, legal standards, and practical barriers that determine whether presidential assertions of power hold up when challenged.

Youngstown Framework for Presidential Power

The most important rule courts use to judge presidential power comes from a 1952 case. President Harry Truman tried to seize steel mills during the Korean War, claiming national security justified his action even without congressional authorization. The Supreme Court said no, and Justice Robert Jackson’s framework from that case—Youngstown Sheet & Tube Co. v. Sawyer—remains the standard courts use today.

Jackson described three levels of presidential power. At the top: actions taken with explicit congressional authorization. The strongest possible legal position. In the middle: actions taken without congressional authorization but also without congressional opposition, where presidential power exists but remains limited. At the bottom: action explicitly contrary to congressional will, where courts give little weight to what the president says.

Potential action on Greenland falls into that weakest category. Congress hasn’t authorized territorial acquisition. Congress almost certainly wouldn’t authorize military action against a NATO ally. And the Constitution explicitly requires congressional involvement in exactly these kinds of decisions.

Presidents do enjoy latitude in responding to genuine emergencies. But that latitude doesn’t extend to permanently altering the nation’s geography or overriding what the Constitution explicitly says Congress controls. The question becomes: what must a president prove to demonstrate that a national security claim justifies unusual actions by the president?

Consider the 2025 tariffs, imposed under the International Emergency Economic Powers Act. The Supreme Court heard oral arguments in November 2025, and justices across the ideological spectrum expressed skepticism about whether the statute grants presidents authority to impose tariffs of “unbounded scope, amount, and duration.” The core concern: whether emergency powers have been interpreted to let the president make laws in a way that violates the system where Congress, the President, and courts each have separate powers.

“Tariff power is a form of taxing power, revenue-raising power, which is part-and-parcel of the legislative domain.” Unlimited tariffs without Congress’s approval let the president raise money that Americans end up paying for—importers and consumers alike. If courts find that national security doesn’t permit presidents to exercise unlimited emergency tariff authority, they’re highly unlikely to permit presidents to acquire territory based on security justifications alone.

War Powers Resolution and Congressional Challenges

The War Powers Resolution, enacted in 1973 after Vietnam, provides specific ways for Congress to challenge unilateral executive military action. Vice President J.D. Vance recently stated that “every President, Democrat or Republican, believes the War Powers Act is fundamentally a fake and unconstitutional law.”

Yet the statute remains on the books. And Congress used it.

In January 2026, the Senate voted 52 to 47 to use the War Powers law to force a vote on whether military action against Venezuela required prior congressional authorization. Five Republicans—Susan Collins, Josh Hawley, Lisa Murkowski, Rand Paul, and Todd Young—voted against their party, joining every Democratic and Independent senator.

The vote demonstrates that congressional ways of taking back control over military decisions aren’t entirely dormant. When military action becomes controversial enough, even some Republicans will use available tools to push back.

For Greenland, these tools would become far more relevant. Taking military action against a NATO ally would trigger immediate congressional and judicial challenges. Danish Prime Minister Mette Frederiksen has stated that if the United States attacked Denmark militarily to acquire Greenland, it would mean “the end of NATO.”

Few members of Congress—Republican or Democrat—would vote to authorize military action that destroys the alliance system the U.S. has built over seven decades. The War Powers Resolution, combined with explicit congressional opposition to NATO’s destruction, creates substantial legal and political barriers to unilateral action.

Threat Assessment vs. Reality

The administration has made specific claims about Arctic threats justifying American control of Greenland. “Right now, Greenland is covered with Russian and Chinese ships all over the place,” came the statement from Air Force One. “There are Russian destroyers, there are Chinese destroyers and bigger. There are Russian submarines all over the place.”

Lin Mortensgaard, an expert on Arctic international politics at the Danish Institute for International Studies, directly contradicted this: “It’s not true.” While Russian submarines do exist across the Arctic region, “there are no surface vessels” near Greenland. China has research vessels in the Central Arctic Ocean, and Chinese and Russian militaries have conducted joint exercises in the Arctic—but closer to Alaska, not in the vicinity of Greenland.

Courts and Congress don’t accept presidential assertions about security threats at face value. They examine whether the claimed threat is real, immediate and serious, and reasonable compared to what the president wants to do. The characterization of Greenland as surrounded by hostile military vessels doesn’t match current intelligence assessments of Arctic military positioning.

Even if the threat were more acute, experts question whether U.S. ownership of Greenland would address it. “We already have everything we want from a security perspective from Greenland, because they’re a member of NATO,” noted Ivo Daalder, former U.S. ambassador to NATO. Seven of the eight Arctic nations are NATO members. The way to improve Arctic security is through NATO, not by acquiring territory by force from an ally.

Existing U.S. Military Access to Greenland

The 1951 Defense of Greenland Agreement, still in effect and frequently renewed, gives American forces extraordinarily extensive access.

The agreement permits the U.S. to deploy forces and equipment widely, prepare and upgrade areas for military use, build and operate bases, station personnel, control military-related air and maritime movements in designated areas, and improve ports and harbors. American military authorities have nearly all the military control they would need, with the exception that it lets Denmark and Greenland stay in charge.

The United States operates Pituffik Space Base (formerly Thule Air Base) in northwestern Greenland, providing missile warning, missile defense, and space surveillance operations for the U.S. and NATO. Experts emphasize that the U.S. has been explicitly invited to expand this presence. “The door is already wide open,” according to Mai’a Cross, political science professor at Northeastern University. “The U.S. has an open invitation to increase the size of its military base and potentially have other military bases there.”

Both Denmark and Greenland have repeatedly stated they would welcome greater U.S. military investment and expanded presence—provided it occurs through cooperation rather than coercion.

The explanation for why American ownership is necessary reveals the distinction between functional capability and what feels right: “You defend ownership. You don’t defend leases.” In an interview with the New York Times, “ownership gives you things and elements that you can’t get from just signing a document.”

Ownership provides the feeling of total control that agreements, no matter how comprehensive, cannot guarantee. The national security argument rests less on current military vulnerability and more on a preference for absolute sovereignty over alliance relationships.

Courts have repeatedly held that while genuine security threats can justify unusual actions by the president, preferences for maximum control or psychological reassurance don’t constitute the kind of compelling, immediate threat necessary to override normal constitutional processes.

Historical Precedent: The Virgin Islands Purchase

The closest historical parallel involves Woodrow Wilson’s administration in 1917, when the United States effectively pressured Denmark into selling the Virgin Islands. As American leaders perceived German threats during World War I, they grew concerned that Denmark might cede Caribbean territories to Germany or that Germany might seize them.

Secretary of State Robert Lansing “suggested that if Denmark didn’t sell [the islands], the U.S. just might go and seize them” to keep Germany out of the Caribbean. Denmark, facing a direct threat backed by American military power, capitulated. The United States purchased the Virgin Islands for $25 million—approximately $600 million or more in today’s dollars.

Yet even this example of coercion reveals constraints. The transfer required a negotiated agreement with Denmark. It required Congressional appropriation of the purchase price. The transaction worked because it involved sale and payment between two governments rather than unilateral seizure.

Such acquisitions aren’t possible today in the same way. The transaction occurred when international law allowed powerful countries to take territory, when NATO didn’t exist, and when the idea that international law should protect smaller countries was still developing. “Today, NATO’s foundation and the UN Charter explicitly forbid acquiring territory by force. Thus, the diplomatic fallout in 2025–26—European Union statements, NATO crisis meetings, public fury—has no parallel in 1917.”

International law has evolved. NATO commitments bind the United States. Congressional attitudes toward territorial expansion have shifted dramatically.

The Venezuela Operation as Precedent

The military operation in Venezuela in January 2026 provides a revealing modern parallel. Military strikes and the capture of Venezuelan President Nicolás Maduro occurred, with claims of power the Constitution gives the president to conduct this military operation as a law-enforcement action.

The operation was extraordinarily successful from a military perspective: more than 200 special operations forces captured Maduro and his wife with no U.S. casualties and minimal harm to civilians or buildings. Yet even this apparent assertion of unfettered executive military authority immediately triggered constitutional challenges.

The Senate War Powers Resolution vote demonstrated that some members of Congress—including five Republicans—believed military action required authorization. The administration felt compelled to justify the operation as law enforcement (capturing someone indicted for drug trafficking combined with terrorism) rather than pure military action, suggesting sensitivity to constitutional concerns about unilateral military action.

Presidents claim broad powers, but they still face limits. They cannot declare something necessary and act unilaterally. They must either work within existing congressional authorization, seek new authorization, justify actions as consistent with constitutional powers, or face vigorous legal and political challenges.

Multiple Constraints on Presidential Power

The ways that limit presidents from grabbing too much power operate on multiple levels simultaneously. At the constitutional level, Congress must authorize any permanent addition to U.S. territory. No emergency provision permits a president to bypass these requirements.

Congress itself has demonstrated willingness to use available tools to challenge executive overreach. The Senate’s War Powers Resolution votes on Venezuela show that members of Congress, including some Republicans, recognize they need to protect Congress’s power on matters of military force.

A hypothetical military action against Greenland would face even more unified congressional opposition. Few members of Congress would vote to authorize military action that would effectively destroy NATO. The political coalition against such action would be far more substantial and bipartisan than coalitions that typically oppose executive military action.

International law and alliance obligations create additional constraints that work separately from the Constitution. NATO’s founding treaty explicitly requires members to settle disputes peacefully and forbids the threat or use of force against other members. If one founding member attacked another, the idea that NATO members defend each other would collapse.

Courts can also enforce these limits. When the tariff actions reached the Supreme Court, justices across the ideological spectrum expressed concern that the administration’s interpretation of emergency powers had gone too far. In a Greenland acquisition case, courts would likely find clearer constitutional violations.

The practical impossibility of sustaining such action without broad political support constitutes a formidable constraint. Even if legal authority existed—which it doesn’t—sustained occupation and integration of Greenland into the United States would require Congressional appropriation of enormous resources, ratification of international agreements, and management of the resulting NATO crisis. Public opposition, allied diplomatic pressure, and congressional budget authority would make such action ultimately unsustainable.

Expansion of Executive Power Claims

The Greenland episode raises questions about whether the administration is pushing boundaries of claimed executive authority beyond precedents even during earlier periods of expansive executive power assertion.

Presidents have long contested constitutional limits on their war powers and national security authority. But openly saying he’d use military force against a NATO ally to acquire territory represents something relatively novel in modern American governance.

President George W. Bush claimed constitutional authority for detention policies and surveillance programs he argued were necessary for counterterrorism, but he sought congressional authorization for military action in Iraq and Afghanistan. President Obama asserted broad authority for drone strikes and other military operations, but he didn’t explicitly threaten military action against NATO allies.

This approach differs in being more openly willing to state that national security concerns justify action “whether they like it or not”—explicitly ignoring what the people there want and what the host nation decides. A special envoy for Greenland has been appointed, showing the administration is serious about taking territory rather than making a rhetorical point. Military options have been explicitly left on the table.

The administration has invoked what it calls the “Trump Corollary” to the Monroe Doctrine, suggesting that strategic regions in the hemisphere fall within an American sphere where the U.S. has the right to determine political outcomes. This rhetorical framework goes beyond previous presidential claims about hemispheric hegemony by explicitly suggesting that territory within the region can be claimed by the United States if strategic circumstances warrant it.

Openly considering military action against NATO members to acquire territory, backed by national security justifications rather than formal legal authorities, does represent claims about presidential power that go further than before.

Constitutional Limits on Executive Authority

The Greenland controversy illuminates a distinction in American governance: the difference between what presidents say they can do and what they can do. The assertion that national security justifies taking action “whether they like it or not” reflects an expansive view of executive authority that finds limited support in constitutional doctrine, historical precedent, or the specific ways Congress has established to check executive overreach.

National security concerns don’t override Congress’s exclusive constitutional authority over territorial matters. The War Powers Resolution provides Congress with ways to challenge unilateral military action. International law and NATO commitments create diplomatic and legal barriers to territorial acquisition from allied nations. Courts have established standards for evaluating whether national security justifications are sufficiently grounded in reality and sufficiently proportional to the action proposed.

Existing security arrangements already provide the United States with the military capabilities experts identify as necessary for Arctic defense. The difference between what the United States already possesses and what the administration proposes to acquire is the distinction between working with allies versus owning the land—between working with allies through NATO and international agreements to address shared security concerns, and attempting to unilaterally control territory.

National security law doesn’t grant presidents authority to pursue the latter when the former already provides genuine defense capabilities.

Presidential power isn’t unlimited, even when national security concerns are genuinely grave. The Constitution’s structure, the specific ways Congress has created to defend its constitutional prerogatives, and the practical requirements of maintaining political support all constrain executive action. Understanding these constraints requires looking at how it works: how courts evaluate emergency claims, when Congress mobilizes to defend its authority, how international law and alliance obligations create independent limits, and what practical factors make sustained executive overreach unsustainable.

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