Why did they claim that the Sugar Act was unjust, and unconstitutional?

Parliament passed 'The Sugar Act of 1764,' levying an import tax on molasses enforced by the admiralty courts. ... The colonists again asserted that the act was an unconstitutional tax, and that it violated English natural rights by trying the colonist without juries.

Explanation:

the historians cited in the article all agree with one another about the cause of the civil war. despite coming from different backgrounds and cultures, the historians agree that slavery was the root cause of the civil war. the fact that all these historiansgenerally agree with one another makes their shared viewpoints more reliable and valid, especially because the historians have different backgrounds and all work for the well-respected institutions of howard university, clemson university, and the university of colorado.