You can't really get around “birthright citizenship” in the Constitution The limits Trump is setting are not unreasonable — but all of us who are born in the United States are citizens by birthright — which we can't deny or sell for a bowl of porridge like Esau.
Trump's authority to pardon “... he shall have Power to grant Reprieves and Pardons for Offences against the United States, except in Cases of Impeachment.”