At least, that was what lawyers from the UK argued during a debate at Philadelphia’s Ben Franklin Hall.
And a cow goes ‘moo’.
Of course the Brits would say the Declaration of Independence was illegal based on what they deemed lawful. The Americans of the time had an entirely different perspective of what was lawful. In the end the Revolutionaries’ viewpoint won out after a lengthy conflict with a combination of foreign assistance (France) and some miscalculations by the British troops/officers when dealing with the Colonies’ civilians and army.
Those in power always claim those who challenge their authority and succeed did so illegally. Even centuries after the fact. For example, both branches of my family could rightly claim that the British Empire illegally forced them to leave their homelands (Scotland and Ireland). What does that accomplish? Nothing. It doesn’t change the fact that my family is here and the old homelands are now viewed as a place to visit to reconnect with our heritage, nothing more.