Like the right of self defense,the right of the people to overthrow a tyrannical government and replace it with a government that restores natural rights, is a perfect right.Like natural rights, perfect rights are prior to constitution and social contract.
From the Declaration:
But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security.