In the Summary Review of the Rights of British America Jefferson sets out many reasons for the necessity of a declaration of independence among which are the despotism of the British crown under George III in preventing the inhabitants of the 13 colonies from the pursuit of "life, liberty and the pursuit of happiness". Also, the colonies had written the king several times about the necessity of redress for their grievances but had never received a response. Also, being a colony of Great Britain, free trade with other countries was not allowed.
The King of Great Britain has no real power over the colonies since they never consented to his authority. People have the right to form their own governments, and the best form of government is a democratically elected one.