What legal steps would Denmark or Greenland take under international law if the US tried to seize Greenland?
Executive summary
If the United States attempted to seize Greenland, Denmark and Greenland would mobilize an array of international‑law and diplomatic tools: immediate protest and mobilization of NATO and UN channels, litigation and requests for advisory opinions at the International Court of Justice (ICJ), coordinated calls for non‑recognition and sanctions via the UN General Assembly and allied governments, and steps to emphasize Greenlanders’ right to self‑determination under Danish law — all while preparing defensive military and allied assistance measures; those options are grounded in the UN Charter’s prohibition on the use or threat of force and in treaties and practice that make forcible annexation unlawful [1] [2] [3].
1. Immediate diplomatic and domestic legal signaling: declare a hostile act and withdraw envoys
Denmark would begin with unequivocal diplomatic acts — declaring any forcible attempt a “hostile act,” publicly condemning violations of sovereignty, withdrawing ambassadors or diplomatically downgrading relations — steps already contemplated in past reporting and hypothetical scenarios where Copenhagen treated sovereignty moves as hostile and recalled envoys [4] [5]; such acts create political record and pave the way for UN and allied action [3].
2. Rapid invocation of NATO channels and Article 5 considerations
Copenhagen would invoke NATO consultations immediately; defense‑law experts note an armed operation to seize Greenland would meet the threshold of an “armed attack” that could trigger Article 5 collective‑defence obligations, though the Alliance’s political decision‑making would be decisive and fraught given U.S. membership and veto power inside the Alliance [2] [3].
3. UN Security Council diplomacy and the limits of enforcement
Denmark would take the case to the UN Security Council demanding condemnation and measures, but practical enforcement faces the reality that the United States could veto substantive Council resolutions; nevertheless Council debate would document illegality and build a record for other international responses [1] [3].
4. General Assembly political pressure and the ICJ advisory or contentious route
With a likely Security Council veto available to Washington, Denmark and allies would push the dispute into the UN General Assembly to secure condemnations, non‑recognition resolutions, and a request for an ICJ advisory opinion or institute contentious proceedings at the ICJ — moves that are politically powerful though not always immediately coercive, and that generate long‑term legal pressure and legitimacy for non‑recognition policies [3] [4].
5. Litigation, treaty law and invalidity of coerced transfers
Legal claims would stress that any transfer obtained by coercion violates peremptory norms (jus cogens) and the UN Charter’s ban on the use of force, would breach human‑rights commitments (e.g., ICCPR Article 1 on peoples’ right to self‑determination cited in reporting), and that treaties or agreements concluded under coercion are invalid under the Vienna Convention on the Law of Treaties — grounds for immediate legal challenge and global non‑recognition [1] [2].
6. Asserting Greenlanders’ self‑determination and internal procedures
Denmark would invoke the 2009 Self‑Government Act and highlight Greenlanders as a people entitled to self‑determination; reporting stresses that a transfer “bypassing their free consent” would breach UN instruments and that domestic Greenlandic consent and possibly a referendum would be central to lawful changes of status [1] [6].
7. Alliances, sanctions and coordinated political‑economic measures
Beyond legal forums, Denmark would marshal EU and allied political support to impose diplomatic isolation and targeted measures; European institutions and states have signaled readiness to back Copenhagen politically and to condemn any US attempt as violating international law, making coordinated sanctions, travel and trade measures and military deployments the likely political toolkit [7] [8] [9].
8. Military preparation, deterrence and practical obstacles
Copenhagen would also prepare military defensive measures and invite allied forces to reinforce Greenland — Denmark has stepped up Arctic defence planning and could increase presence while relying on NATO frameworks — but practical deterrence is constrained by the balance of U.S. power and the political complexity of asking NATO to act against one of its own members [6] [10] [3].