A nation of laws” means that laws, not people, rule. Everyone is to be governed by the same laws, regardless of their station; whether it is the most common American or Members of Congress, high-ranking bureaucrats or the President of the United States; all must be held to the just laws of America. No one is, or can be allowed to be, above the law.
This idea was paramount in the complex process of establishing the United States of America, a young nation whose brave leaders had put everything on the line to escape the tyranny and oppression of the British Crown, which at the time was a nation ruled by people, in the person of King George III.
The Founders wrote restrictions into the Constitution against bills or laws of attainder, which are laws that do not apply equally to everyone, but target specific persons or groups in their enforcement, and are also known as “bills of pains and penalties.” In the hands of corrupt officials, these laws could be used as a weapon that would give an incumbent politician a major advantage over anyone else.
