1. United States
2. Mass.
3. Letter

President Donald J. Trump has escalated from inflammatory rhetoric to explicit threats against a NATO ally and its autonomous territory, Greenland. These threats now include economic coercion, alliance pressure, and refusal to rule out the use of force. Congress must intervene immediately. Multiple outlets, including Bloomberg, PBS NewsHour, the BBC, and The Atlantic, have confirmed the authenticity of a message distributed by the U.S. National Security Council to European governments, originally sent by President Trump to Norway’s prime minister. In that message, the President asserted that the United States must have “complete and total control of Greenland,” rejected Denmark’s sovereignty over the territory, and explicitly linked his foreign-policy posture to resentment over not receiving the Nobel Peace Prize. These claims are demonstrably false and profoundly dangerous. Greenland is a self-governing territory within the Kingdom of Denmark, a founding member of NATO. Danish sovereignty over Greenland is well established in international law and has been formally recognized by the United States for decades, including through bilateral defense agreements. The President has justified his threats by claiming Greenland must be seized to prevent Russian or Chinese aggression. This argument is fundamentally incoherent. Greenland is already protected by NATO. The entire purpose of the alliance is collective defense: any attack on Denmark or Greenland would trigger a unified response. By threatening a NATO ally, the President is not strengthening deterrence—he is destroying it. If the United States attacks or coerces its own allies, the alliance ceases to function, and the very risks the President claims to fear become more likely, not less. The President has also confirmed his intent to impose tariffs on allied nations and to use NATO obligations as leverage for territorial demands. European leaders and industry groups have warned that these actions risk a trade war and permanent damage to transatlantic security cooperation. Denmark has now begun reinforcing its military presence in Greenland in response to U.S. threats—an extraordinary and alarming development between allies. Congress cannot dismiss this as bluster. The Constitution assigns Congress authority over war, trade, and appropriations precisely to prevent reckless or personal decision-making from dragging the nation into conflict. Allowing a president to threaten a NATO ally with force or economic punishment based on personal grievance places the United States on a path toward isolation, instability, and long-term loss of credibility. We therefore urge Congress to act immediately by: 1. Publicly repudiating any attempt to seize or coerce control over Greenland. 2. Passing legislation or a War Powers resolution prohibiting the use of U.S. forces against Denmark or Greenland without explicit congressional authorization. 3. Blocking funding for any military, intelligence, or economic action intended to pressure Denmark or Greenland. 4. Holding immediate oversight hearings on the President’s conduct, decision-making, and fitness with respect to foreign policy and national security. 5. Reaffirming U.S. commitments to NATO and the post–World War II rules-based international order. Silence now would constitute acquiescence. History shows that unchecked executive power in foreign affairs leads not to strength, but to catastrophe. Congress is the last constitutional guardrail. It must act.