TIME spoke to legal experts about whether Trump could legally pull the U.S. out of NATO and the wider implications.

Donald Trump’s attempt to strongarm Denmark and Europe into accepting the annexation of Greenland is a disgraceful betrayal of the Western alliance, a foolish misunderstanding of the American national interest,

U.S. NATO ambassador Matthew Whitaker defends American focus on Greenland amid European backlash, calling Arctic security crucial for continental defense.

Denmark’s Prime Minister Mette Frederiksen has issued one of her strongest public warnings yet. This comes after US President Donald Trump renewed his controversial claims over Greenland. Frederiksen’s message was clear and serious.

The Trump administration has repeatedly said the U.S. should be in control of Greenland, which is part of Denmark and NATO.

Trump has said he wants the territory because of its strategic location. Maps show how a melting Arctic is affecting geopolitics.