A Century Old U.S. Promise Stands in the Way of Any Bid for Greenland

 President Donald Trump has revived interest in acquiring Greenland, he ran headlong into a century old diplomatic commitment that continues to bind the United States. Known as the 1916 Lansing Declaration, the document quietly but firmly limits what any American president can legally do when it comes to Greenland.

The declaration dates back to World War One, when the United States was negotiating the purchase of the Danish West Indies, now the U.S. Virgin Islands. During those talks, U.S. Secretary of State Robert Lansing issued a formal diplomatic statement recognizing Denmark’s full and permanent sovereignty over Greenland.

That recognition was not symbolic. It was a condition of the deal. Denmark agreed to sell its Caribbean territory only after receiving explicit assurance that the United States accepted Danish control over Greenland. The agreement was finalized in 1917 and ratified by the U.S. Senate, giving it the force of binding international law.

For more than a century, that recognition has stood unchallenged. Under international legal principles, especially the doctrine of estoppel, a country that formally recognizes another nation’s sovereignty cannot later reverse its position without violating its own commitments. Legal scholars note that this makes any unilateral U.S. claim to Greenland legally indefensible.

The declaration also reinforces modern international law. The United Nations Charter prohibits the acquisition of territory by force or coercion, and Greenland today enjoys broad self government within the Kingdom of Denmark. Since 2009, Greenlanders have had the recognized legal right to vote for independence, placing decisions about the island’s future firmly in the hands of its people.

That reality sharply narrows the options available to any U.S. president, including Trump. A direct purchase of Greenland would require consent from Denmark, approval by Greenland’s government, and likely a public referendum among Greenlanders themselves. It would also need congressional approval in Washington. Politically, such a scenario is widely viewed as unrealistic.

What remains possible is influence rather than ownership. The United States already maintains a strategic military presence at Thule Space Base and continues to deepen defense cooperation with Denmark and Greenland. Washington can also invest in infrastructure, support economic development, and counter growing Chinese and Russian interest in the Arctic through diplomacy and trade.

Another theoretical path would involve supporting Greenland’s independence from Denmark. If Greenland were to become a sovereign state by popular vote, the United States could then negotiate treaties or strategic agreements with it. Even then, annexation would remain off the table without Greenland’s clear consent.

In practical terms, the Lansing Declaration ensures that Greenland cannot be taken, pressured, or claimed without violating long standing U.S. commitments and international law. While presidents may talk boldly about strategic interests in the Arctic, the legal boundaries were drawn more than a hundred years ago and they remain firmly in place today.