As a Presidential commutation is simply a mitigation of punishment, it does not set aside the initial judicial sentence, and therefore does not establish separate grounds for a habeas petition; a petition is therefore considered a second or successive challenge to the initial judicial sentence. Similarly, the commutation cannot shift the sentence from one based on a statutory minimum to one based on a gudelines range, making the sentence susceptible to a challenge based on a subsequent revision of the guidelines.
http://cdn.ca9.uscourts.gov/datastore/opinions/2018/07/13/16-10499.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.