Explained: Can the US legally acquire Greenland without using force?

As Donald Trump revives talk of acquiring Greenland, here's explaining on whether the US can legally buy the island, what international law allows, and why Europe is pushing back

US President Donald Trump has once again highlighted his desire to acquire Greenland, with the White House confirming that his administration is weighing “a range of options”, including the use of military force. The remarks have framed Greenland as a “national security priority” for the United States, triggering a sharp and unusually united response from Europe.

 

Denmark, which retains control over Greenland’s defence and foreign policy, has rejected the idea outright, as have the Arctic island’s own leaders. Within hours, key European allies rallied behind Copenhagen, warning against any move that would breach sovereignty or violate the UN Charter.

 

For decades, the US has expressed strategic interest in Greenland, the world’s largest island, rich in minerals and positioned at the gateway to the Arctic. According to a Wall Street Journal report, US Secretary of State Marco Rubio told lawmakers at a classified briefing on January 5 that the administration was planning to “buy” the island from Denmark.

 

With military action widely condemned by allies and international law experts, what non-coercive pathways exist, and how realistic are they?

 

What is Greenland’s legal status?

 

Greenland is a self-governing territory within the Kingdom of Denmark. While it manages its internal affairs, Denmark remains responsible for its defence, foreign relations and international representation.

 

The island’s current legal status was formalised in 1953 and expanded through home rule in 1979 and self-rule arrangements in 2009, which recognised Greenlanders as a people with the right to self-determination and left open the possibility of future independence.

 

With a population of around 57,000, Greenland has extensive autonomy. Any change in sovereignty would require amendments to Denmark’s constitutional framework and explicit consent from Greenland’s elected government and population.

 

Does international law allow a takeover without force?

 

International law places strict limits on territorial change. Article 2(4) of the United Nations Charter prohibits the threat or use of force to acquire territory. Modern legal doctrine treats conquest and annexation as illegitimate, regardless of domestic declarations.

 

The only lawful pathway is territorial cession through a free and voluntary treaty between sovereign states. Such a transfer must not be coerced and must respect the right of self-determination of the affected population.

 

At present, Denmark and Greenland have categorically rejected any sale. Greenland's leaders have repeatedly said the island “is not for sale” and that its future must be decided democratically by its people.

 

How much money has been discussed to buy Greenland?

 

Although Rubio has floated the idea of “buying” Greenland, there is no official price under discussion because neither Denmark nor Greenland is willing to negotiate a sale.

 

Speculative estimates by media outlets and think tanks include:

 

• A 2019 Washington Post analysis suggested a notional range from $200 million to $1.7 trillion, with a midpoint of about $42.6 billion, based on Alaska and resource valuations
• A New York Times estimate in 2025 placed a hypothetical price between $12.5 billion and $77 billion, using GDP-adjusted comparisons
• The Financial Times suggested Greenland’s mineral wealth could justify a valuation of about $1.1 trillion

 

These figures remain academic, as no negotiations are underway.

 

What legal provisions govern territorial changes in US Constitution?

 

The US Constitution does not explicitly outline a mechanism for acquiring foreign territory. However, historical practice provides a framework.

 

Under Article II, Section 2, the president may negotiate treaties with foreign governments, subject to Senate approval. Major territorial acquisitions, such as the Louisiana Purchase in 1803 and the Alaska Purchase in 1867, were carried out through treaties.

 

Following any treaty, the Congress must pass legislation to integrate the territory, determine its governance and appropriate funds.

 

There is no constitutional provision allowing a US president to unilaterally acquire foreign land. Any lawful acquisition presumes a willing sovereign partner, which is absent in the Greenland case.

 

What are the historical precedents?

 

The US has expanded territory without war through negotiated purchases, including:

 

• The Louisiana Purchase (1803), which doubled US territory after acquiring land from France for $15 million
• The Alaska Purchase (1867), when the US bought Alaska from Russia for $7.2 million
• The purchase of the Danish West Indies, now the US Virgin Islands, from Denmark in 1917 for $25 million

 

Each case involved treaties and the consent of the selling sovereign.

 

What's next?

 

None of the legal prerequisites exist for Greenland to become US territory. Denmark and Greenland both assert sovereignty and reject sale. Danish Prime Minister Mette Frederiksen has said that any attempt for forced takeover of Greenland would mark the end of NATO and with it, "the security that has been established since the end of the Second World War".