I don’t think this is a case of Obama issuing pardons. These guys served out their prison sentences.
Pelton was tried and convicted of espionage in 1986 and sentenced to three concurrent life sentences and a fine. If they had wanted to keep him in prison, they could have. The decision was made to let the guy walk out.
Pollard was given a full life sentence. In 2015, they decided to parole him. Again, if they wanted to keep him in, they could have. The decision was made to let the guy walk out. The Justice Dept had a chance to appeal the parole, and they did not.