Isn't that basically an act of war? Or something just short of it? I can't remember another time when one country threatened to enter another country's embassy without an invitation... Have there been other cases like this in recent history??
"The law which Britain is threatening to invoke in the Assange case is the Diplomatic and Consular Premises Act 1987.
It allows the UK to revoke the diplomatic immunity of an embassy on UK soil, which would potentially allow police to enter the building to arrest Mr Assange."
If they do that it wouldn't be an act of war, it would be legal. It definitely sets a terrible precedent though and even if it's legal Ecuador might interpret it as an act of war.