After Parliament repeals the Stamp Act, they come back and say that Parliament DOES have the right to tax colonists with
which Act?

The answer is the Declaration Act

Explanation:

The end of the Stamp Act did not end Parliament's conviction that it had the authority to impose taxes on the colonists. The British government coupled the repeal of the Stamp Act with the Declaratory Act, a reaffirmation of its power to pass any laws over the colonists that it saw fit

a countries leader should be motivated by the common good of the country.