NATO’s Greenland Crisis Exposes a Fatal Blind Spot in Alliance Law

The legal fragility of the alliance is stark. Article 5 mandates that an attack on a member’s territory in North America constitutes an attack on all, yet the treaty contains no mechanism to address an aggressor who is also a member. Scholars point out that a U.S. seizure of Greenland would trigger a mutual defense obligation against the United States itself—a scenario the 1949 founders never envisioned. Because the North Atlantic Council operates on consensus, Washington effectively holds a veto over any collective response aimed at its own actions, rendering the treaty’s guarantees more of a formality than a functional deterrent.

Denmark’s reaction to recent threats from the Trump administration—which included economic tariffs and claims of ownership over the territory—highlights this power imbalance. Rather than invoking Article 4 for formal consultation, Copenhagen chose to bolster its own defense spending and rely on back-channel diplomacy. This reluctance to use internal mechanisms mirrors historical precedents like the Cod Wars or the 1974 Cyprus crisis, where intra-alliance disputes were resolved through political friction and external mediation rather than treaty law. The Arctic Sentry mission is a strategic stopgap, but it underscores a reality that the alliance is desperate to ignore: when the dominant member acts as the aggressor, NATO’s founding documents provide no legal recourse, only the hope that political costs at home will act as a sufficient brake.