It's been 235 years, and the British still aren't over the Declaration of Independence. A bunch of American and British lawyers had a debate in Philadelphia recently over whether the declaration was "legal." The British viewpoint:
The Declaration of Independence was not only illegal, but actually treasonable. There is no legal principle then or now to allow a group of citizens to establish their own laws because they want to. What if Texas decided today it wanted to secede from the Union?