A banner in support of Julian Assange is seen on a barrier across the street as police officers stand guard at the Ecuadorian Embassy in central London, London, Wednesday, Aug. 15, 2012. WikiLeaks founder Julian Assange entered the embassy in June in an attempt to gain political asylum to prevent him from being extradited to Sweden, where he faces allegations of sex crimes, which he denies. (AP Photo/Sang Tan)

LONDON - It is an inviolable diplomatic principle: British law and the British police cannot reach inside the embassy of a foreign country.

But Ecuador says British officials have threatened to march in and grab WikiLeaks founder Julian Assange from its London embassy, where he has been holed up in a bid to escape extradition to Sweden over sex crimes allegations.

WHAT HAS BRITAIN SAID?

Under the 1961 Vienna Convention on Consular Relations, diplomatic posts are treated as the territory of the foreign nation.

But in a letter to Ecuadorean officials, Britain cited a little-known law, the Diplomatic and Consular Premises Act of 1987, which it said would allow it to arrest Assange within the embassy premises.

The law gives Britain the power to revoke the status of a diplomatic mission if the state in question "ceases to use land for the purposes of its mission or exclusively for the purposes of a consular post" — but only if such a move is "permissible under international law."

In its letter, Britain adds, "We very much hope not to get to this point."

WHEN WAS THIS LAW PASSED?

The law was passed after the 1984 siege of the Libyan embassy in London, which was sparked when someone inside the building fatally shot a British police officer, Yvonne Fletcher. An 11-day standoff ended with Britain severing diplomatic relations with Libya and expelling all its diplomats.

The Associated Press could find no record of the law ever being used to justify forcible entry into an embassy.

SO CAN BRITAIN GRAB ASSANGE?

Many legal experts are skeptical. The diplomatic fallout would be immense, leaving British missions around the world vulnerable to reprisals.

And lawyers say a British court would likely be unwilling to sanction a raid on the embassy.

The law was intended for situations in which a diplomatic mission was being used for serious wrongdoing such as terrorism. Sheltering Assange hardly compares.

Former government lawyer Carl Gardner says a court would likely rule that using the law against Assange would be inconsistent with the intent of the law.

"I don't see it as a realistic prospect that the government would do a dash for the airport with him," he said.

WHAT HAPPENS NEXT?

Ecuador announced Thursday that it has decided to grant Assange asylum — but that does little to resolve the standoff.

Britain says it has a legal duty to extradite the 41-year-old Australian to Sweden, regardless of what Ecuador decides. If he emerges from the embassy, he will be arrested, which seemingly makes it impossible for him to get to an airport and travel to Ecuador.

Britain says it wants to find a diplomatic solution, but with Ecuador enraged, that looks farther off than ever.

News from © The Associated Press, 2012