The American colonists were justified in doing this simply because their colonies had become too big and too important to be treated as a colony by the British. The British should have given the colonies some autonomy, but they did not. The analogy I like to use is that of teens and their parents. Parents have to give teens more independence as they grow up. If they do not, the teens may justifiably rebel.
The British were not, on the whole, brutal or oppressive towards the colonists. However, they would not let the colonists have much in the way of self-rule. This had been fine when the colonies were still small and economically weak. By the 1760s and 1770s, however, the colonies were "teenagers." They were big and strong enough to expect some autonomy. When Britain reacted to requests for autonomy by being more strict, the colonists were justified in rebelling.
Clause 38 of the Magna Card says as follows : In future no official shall place a man on trial upon his own unsupported statement, without producing credible witnesses to the truth of it. The Magna Carta is a cedula that King Juan "without land" of England granted to the English nobles in which he undertook to respect the privileges and immunities of the nobility.
