In 1982, the United Kingdom, led by Prime Minister Margaret Thatcher, went to war with Argentina over the Falkland Islands in the South Atlantic.

Unprovoked, Argentina had invaded and occupied the islands for two months. Against the odds, Mrs. Thatcher assembled a naval task force and deployed it to the South Atlantic to liberate the islands’ British inhabitants. In a victory for self-determination, the British promptly expelled the Argentine invaders.

Three decades later, things are heating up once again in the South Atlantic.

Over the past few months, Buenos Aires has become more aggressive over the Falkland Islands. The Argentine navy has intercepted and even boarded European fishing vessels operating under licenses issued by the Falkland Islands. At Argentina’s behest, more and more South American ports are banning Falkland-flagged ships. Just last week, two cruise ships were denied a port call in Argentina because they previously had visited the Falklands.

Argentina also has publicly blamed the British for the “militarization of the South Atlantic.” The “militarization,” however, was merely the routine deployment of a British warship to the South Atlantic and the arrival of Prince William on the islands for duty as a search-and-rescue pilot. In this role, he could be rescuing Argentines as easily as Falklanders - hardly provocative.

The United Kingdom wants to let the Falklanders decide the status of the Falklands. Unfortunately, Argentina would like to annex and colonize the islands. Exacerbating the problem, the Obama administration has stated publicly that it would like the United Nations to oversee negotiations on the future of the islands’ inhabitants. This policy plays right into the hands of Buenos Aires and makes a mockery out of the “special relationship” between the United States and Great Britain.

So what does history suggest regarding the status of the Falkland Islands? The first known landing there was made in 1690 by a British naval captain, John Strong. At that time, the islands were named after Viscount Falkland, a prominent British lawmaker. The British, French and Spanish all had settlements on the islands at various points until the last European settlement was abandoned in 1811, leaving the Islands uninhabited. In 1833, the British re-established a settlement, which has been there ever since.

The strongest argument the United Kingdom has for its claim on the Falkland Islands is the inhabitants’ right to self-determination. The 3,000 residents overwhelmingly want to be British and not Argentine. Linguistically, culturally and historically, nobody can deny that they are British. The right to self-determination is guaranteed by the United Nations Charter and the International Covenant on Civil and Political Rights - and Argentina is a signatory to both.

Argentina’s claim to the Falkland Islands is based on two points: the principle of uti possidetis juris and the geographical contiguity of the islands in relation to Argentina. Uti possidetis juris is the belief that upon being granted independence, newly formed states should inherit the same borders that their former colonial masters had.

Uti possidetis juris is not a universally accepted principle of international law. Even if it were, it would not apply here because at the time Argentina declared independence from the Spanish Empire in 1816, Spain did not have de facto control of the islands. The last Spanish settlement left the Falkland Islands in 1811.

The geographical contiguity argument is even more ridiculous. Based on this argument, Morocco could have a claim over the Canary Islands or the United States over Cuba, for example.

For its part, the Obama administration needs to make it crystal-clear that it backs the United Kingdom over Argentina regarding the status of the Falklands. Britain is America’s No. 1 ally and contributes more to global security than Argentina ever will.

The administration also needs to reverse its position on U.N. mediation over the status of the islands. Why should the United States, as a nation with a deep-seated tradition of individual rights and instinctive suspicion of the United Nations, want the U.N. to decide the fate of the islanders?

When President Obama hosts British Prime Minister David Cameron this month, he should offer assurances of U.S. military support for the United Kingdom in the event of a crisis - at a minimum, on the same level as provided during the 1982 Falklands War.

The Falklands are British. President Obama should not forget this, and Mr. Cameron should be quick to remind him.

Luke Coffey is the Margaret Thatcher Fellow at the Heritage Foundation.