SSA, FRCP
As the question of retroactive application of a claims adjudication does not present an objective nondiscretionary agency duty, Federal jurisdiction under the mandamus statute is improper.
No equal protection or due process claim, as rules on retroactive application constitute a legitimate procedural bar, and plaintiffs did not challenge constitutionality of old rule in initial proceeding.
http://media.ca8.uscourts.gov/opndir/16/01/143220P.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.