We live in a country under a system of laws, both state and federal. The provisions of those laws are specific. Federal law specifically defines offenses that make someone a federally prohibited person. One of those definitions incorporates certain types of state offenses as a trigger that makes someone a "federally prohibited person".
The president doesn't get to just decree whatever he wants. The Constitution allows for pardons of federal crimes, not state crimes. The definition of "federally prohibited person" is not in itself a crime that someone can be pardoned from. There is no provision of federal law that gives the federal executive branch any leeway in changing someone's characterization as a federally prohibited person based on a state conviction that renders them a federally prohibited person. Period.
There is a "bail-out" provision that allowed federal felons to petition the ATF for an individualized determination to release them from federal PP status if their status was based on a federal crime, but it has been blocked in appropriations bills starting in the 90's, is functionally defunct today, and never applied to state crimes anyway.
If you want to be released from a federal PP status that's based on a state crime, your only recourse today is judicial review from the state that convicted you, executive clemency from that state, or (possibly) an individual lawsuit in federal District Court based on 2A. The federal executive branch cannot help you.
