That was my take, too. After all, how can you be pardoned before trial if you’re presumed innocent?
The US President can, and does, do so. Ford pardoned Nixon, for example.
The President’s power of pardon is one of the few in the Constitution with no check or balance. Obama could, if he chose, empty the federal prisons tomorrow, or let just the black inmates go. The only recourse anybody would have is impeachment, and that wouldn’t put the inmates back in prison.
Read a book where a massive terrorism campaign in America caused Congress to pass a law declaring all politically-motivated violence to be a federal crime, the law subsequently upheld by the Supremes.
The President then started pardoning, before trial, those who murdered his political opponents and critics: judges, congressmen, journalists, academics, etc. The President thus gained power of life and death without appeal over his enemies, and perfectly constitutionally, too.
In this case the President was a rightie, or more accurately a lunatic posing as a rightie. But the procedure could be applied by a leftist equally well.
The presently unrestrained constitutional power of pardon is potentially a real problem.