Why according to Dickinson was it unconstitutional for parliament to tax the colonists?

According to John Dickinson, it was unconstitutional for Parliament to tax the colonists because they were not directly represented in Parliament, violating the principle of "no taxation without representation." He argued that only colonial assemblies had the authority to impose taxes on the colonists, as they were the ones elected by the people who would bear the burden of such taxes. Dickinson believed that Parliament's attempts to tax the colonies were illegitimate and infringed upon their rights as English subjects.