All the acceding States, when they come into the Federation, form part of the Union, accepting the operation of Federal Laws in their States. They accept to that extent that the Federal Government is supreme in the sphere of Federal Law and the President, as representing the Federal Government, can alone be the last, and also the first authority who can grant reprieve or pardon. That is why in the American constitution as is well known, the President has been authorised to grant reprieve or pardon for offences against the United States.
