Let’s test that hypothesis with an absurd example. Suppose Ozero says “I’ll pardon anyone convicted of murder in the future”. What stops him?
Presidential pardons apply only to federal crimes. Very few murders are federal crimes.
“Suppose Ozero says “I’ll pardon anyone convicted of murder in the future”.”
The president can’t pardon future crimes. He can pardon past crimes before the initiation of legal proceedings.
Meaning, he can pardon Hillary for past crimes before she is charged or indicted.
It has to be a federal crime. Murder is almost always a stare level crime.