The Maduro capture gives credence to Trump’s own subsequent boast that when he is exercising his commander in chief authority, he is constrained by no law, but only by “his own morality” – whatever that might be. Indeed, Maduro’s capture constituted an act of military aggression and the initiation of an international armed conflict, all in violation of the U.N. Charter’s prohibition against the non-authorized use of force. It also runs against more than 80 years of U.S. post-war diplomacy designed primarily to create and reinforce a rules-based international order geared to the prevention of war. In ordering the capture, Trump also disregarded Congress’s constitutional authority to declare war and the related consultation requirements imposed by the War Powers Act. His statements regarding Greenland constitute clear signals of his determination to continue with his scofflaw behavior.

Unfortunately for Trump’s imperial ambitions – but fortunately for the rule of law, the U.S. national interest, and international stability – Trump’s ability to execute any act of military aggression against Greenland is constrained by an additional statute: 22 U.S.C. 1928f. This statute – which was not applicable to Venezuela because it is not a NATO member — was adopted by Congress pursuant to Section 1250A of the 2024 National Defense Authorization Act and was designed to prohibit the president from materially altering the U.S. government’s relationship with NATO and the North Atlantic Treaty (the diplomatic instrument that gave rise to NATO) without prior congressional approval. 

How Section 1928f Applies to the Use of Force against Greenland

In addition to its consultation and notification requirements, the statute – which is titled “Limitation on Withdrawal from the North Atlantic Treaty Organization” – contains two principal provisions: first, as the title implies, a broad prohibition against withdrawal from NATO or taking other analogous steps that would materially damage the U.S. relationship with the organization and, second (and critically), a limitation on the use of appropriated funds such that the president would be precluded from using such funds to implement the actions prohibited by the statute. 

The texts of these two provisions are the following:

§ 1928f. Limitation on withdrawal from the North Atlantic Treaty Organization

(a) Opposition of Congress to suspension, termination, denunciation, or withdrawal from North Atlantic Treaty

The President shall not suspend, terminate, denounce, or withdraw the United States from the North Atlantic Treaty, done at Washington, DC, April 4, 1949, except by and with the advice and consent of the Senate, provided that two-thirds of the Senators present concur, or pursuant to an Act of Congress.

(b) Limitation on the use of funds

No funds authorized or appropriated by any Act may be used to support, directly or indirectly, any decision on the part of any United States Government official to suspend, terminate, denounce, or withdraw the United States from the North Atlantic Treaty, done at Washington, DC, April 4, 1949, except by and with the advice and consent of the Senate, provided that two-thirds of the Senators present concur, or pursuant to an Act of Congress.

The applicability of this statute stems from Greenland’s status as an autonomous territory within the Kingdom of Denmark and Denmark’s status as a member of NATO. As Mike Schmitt has explained, “[i]t is clear that Greenland falls within the geographical coverage of Article 5.” 

While the administration will undoubtedly claim that, because it has no intent to formally “withdraw” from the North Atlantic Treaty, the statute is not applicable to the current situation, this assertion would be false. A U.S. attempt to seize Greenland militarily would constitute an attack on Denmark and, through the operation of Article 5 of the North Atlantic Treaty, an attack on each of the other 30 NATO members (excluding of course the U.S.). Not only would this attack instantaneously breach, either directly or constructively, each of the four prohibitions in clause (a) of Sec. 1928f (meaning it would invariably constitute or lead to the suspension, termination, denunciation, and withdrawal of the U.S. from the Treaty), it would necessarily also lead to the destruction of the organization in its current form as the U.S. wages war on our former allies. 

Because these consequences are inevitable, any order by President Trump to launch an attack on Greenland necessarily triggers the automatic cutoff of authorized or appropriated funds that would be required to execute the assault. In addition, because the administration has clearly not only engaged in “deliberation” about taking military action against Denmark and NATO, but, indeed, has reportedly already ordered that military planning be initiated, the consultation and notification requirements of Sec.1928f have already been triggered.  

The consultation and notification requirements are:

(c) Notification of Treaty action

(1) Consultation

Prior to the notification described in paragraph (2), the President shall consult with the Committee on Foreign Relations of the Senate and the Committee on Foreign Affairs of the House of Representatives in relation to any initiative to suspend, terminate, denounce, or withdraw the United States from the North Atlantic Treaty.

(2) Notification

The President shall notify the Committee on Foreign Relations of the Senate and the Committee on Foreign Affairs of the House of Representatives in writing of any deliberation or decision to suspend, terminate, denounce, or withdraw the United States from the North Atlantic Treaty, as soon as possible but in no event later than 180 days prior to taking such action. [Emphasis added.]

It has not been reported that the Trump administration has yet complied with either of these two statutory requirements. If that is the case, it is already in breach of them.

The Constitutional Dimension

The division of constitutional authorities between Congress and the Executive in foreign affairs, including the authority to withdraw from treaties (on which the Constitution is silent), has historically been a matter of legal dispute between the two political branches. While this is a complex topic and the executive branch has been accorded great deference in the post-ratification management of treaties, with respect to the North Atlantic Treaty there is a strong argument that Congress’ assertion of a measure of legislative control so as to protect the U.S.-NATO relationship should be given preeminence over the administration’s intent to destroy the organization. 

First, Congress has a long history of deep and consistent legislative involvement in the U.S.–NATO relationship generally and with the North Atlantic Treaty specifically. Second, according to the Congressional Research Service in a Jan. 6, 2025, Legal Sidebar, the enactment of Section 1928f “is the first statute in which Congress has prohibited unilateral presidential withdrawal from a treaty.” And third, Congress has coupled its treaty termination prohibition with the Section 1928f(b) limitation of funds provision, thus coupling its unchallengeable constitutional power of the purse with the legislation designed to protect NATO. 

These factors led the CRS to conclude that if the Trump administration were to refuse compliance with the Section, it may well find that its presidential power relative to that of Congress is at “at its lowest ebb” under the Youngstown framework. Thus, if Congress were to seek to challenge Trump’s aggressive designs on Greenland, the invocation of Section 1928f would provide a strong foundation for the challenge.

Moreover, as practitioners and scholars have argued, the North Atlantic Treaty’s status as an advice-and-consent treaty and its subject matter also counsel towards congressional authority to regulate withdrawal, suspension, or denunciation: 

As the North Atlantic Treaty is an Article II treaty adopted with two-thirds approval by the Senate, requiring congressional authorization for withdrawal places limitations on withdrawal that are consistent with the degree of authorization needed to enter the treaty. Such limits are also consistent with the subject matter of the treaty, which relates to the war powers shared between Congress and the president.

The Reaction of Denmark, Greenland, and Other European Countries

The governments of both Denmark and Greenland have repeatedly stated that they oppose the annexation or sale of Greenland to the United States, a stand that is reinforced by a large majority of the public, as evidenced by public opinion polls in both countries. In addition, Denmark has announced that it is bolstering its military presence in Greenland and will consult with European allies to potentially solicit additional military support. Sweden, France, and Germany have already sent troops and the U.K. is considering it. Other EU-member countries, such as Spain and Italy, while not yet committing troops to Greenland have condemned the threatened aggression.

Danish authorities have stated that they would fight back if invaded. 

The Foreign Policy and National Security Dimensions

The repercussions of Trump’s threats against Greenland and Denmark have already been severe inasmuch as they have demonstrated to NATO and all other European nations that the United States cannot be trusted as an ally, partner, or even a good neighbor; and, worse, that the United States actually presents a military threat. 

Should the United States actually seek to accomplish its Greenland landgrab, the consequences would be infinitely worse. With NATO shattered, the European Union – along with the U.K. and Canada – would likely react by summarily: terminating all military and intelligence cooperation; closing its airspace to U.S. flights; terminating all U.S. basing rights in their territories; detaining and disarming all U.S. military personnel and assuming custody of all U.S. military equipment; and interning all U.S. intelligence, diplomatic, and other personnel. 

Beyond those immediate security consequences, economic sanctions would be levied quickly, financial cooperation and European investment in U.S. debt instruments would plummet, and Europe would seek to lessen its dependency on the dollar. Sales of U.S. products or services to Europe would sharply decline, including sales of military weapons, and the U.S. defense industry would shrink. Tourism in both directions would also decrease. There will be global economic repercussions as well. And this would only be the start.

As harmful as these security and economic countermeasures may be to the United States, the negative impact of U.S. aggression may even be worse across the Atlantic. Beyond the damage to Denmark, the most immediate impact will be felt in Ukraine and Europe as a whole. While President Trump insists that U.S. possession of Greenland is imperative for the protection of the U.S. and Europe from encroachments by China and Russia, that claim is bogus. 

In business terms, the value proposition that President Trump seems to be advancing is the following: The United States will acquire Greenland, which although vast, is barren and frozen, for the costs of waging a war of aggression on Denmark and Greenland; destroying NATO; severing our economic, military, and political relationship with the EU, the U.K., and Canada; enduring economic and commercial sanctions; and abandoning the heretofore fruitful collaborative effort to build a rules-based international order. If this is the proposed deal, most Americans will have no trouble concluding that it is a fool’s bargain, particularly from a security standpoint. 

To be clear, the principal beneficiary of Trump’s aggression will be Russia, which will no longer have to contend with NATO’s defensive barrier. What Trump has actually done by threatening Greenland and Denmark is to open up a “second front” to help relieve the pressure on Russia’s military, finances, and society created by Ukraine’s stout defense of its sovereignty and by the growing European support for Ukraine. Trump’s threats to Greenland both complicate Ukraine’s effort to strengthen its supply chains to compensate for the decrease in American support and Europe’s effort to rebuild its own military (in light of the growing U.S. indifference to Europe) and to simultaneously increase its level of support to Ukraine. 

Ironically, Trump’s second front mirrors the second front launched by Roosevelt and Churchill during the Second World War, with the difference being that the Allies launched D-Day to help save democracy while Trump’s assault is designed to advance autocratic objectives that are inimical to America’s national interest but congenial to Russia’s imperial ambitions. If Russia continues to advance, Europe may well be faced with the very difficult choice of allowing Russia to absorb Ukraine or, instead, to integrate Ukraine and its very capable military into Europe and enter into the defensive war against Russia on Ukraine’s side. This could spiral into an even more dangerous global war. If it does, the Trump administration will share a very large portion of the blame.

Conclusion and Recommendation

President Trump’s threats of military aggression towards Greenland and Denmark are madness. If carried through they will betray American values, make the world less safe, shatter NATO, destroy our historic relationship with our European partners, and cause other incalculable damage to the U.S. national interest. Congress should immediately wrestle from the president his power to launch his threatened unprovoked, unauthorized, and pointless war of aggression against NATO. It can do so by depriving him of the financial means to do so by triggering the application of 22 USC 1928f and ensuring that the administration complies with its requirements.

The post How Congress Can Preserve NATO and Greenland: Using 22 USC 1928f to Protect the Peace appeared first on Just Security.