May state law doctrines of judicial convenience be raised against a preemptive federal statute?

QUESTIONS PRESENTED 1. May state law doctrines of judicial convenience, like res judicata and collateral estoppel, be raised against a preemptive federal statute, 38 U.S.C. § 5301, which voids from inception any and all agreements made by a disabled veteran to dispossess himself of his federally protected veterans’ disability benefits? 2. Even if a state court may raise such state law doctrines, does a disabled veteran have a continuing obligation to use his restricted disability pay to satisfy such an agreement, where 38 U.S.C. § 5301 explicitly prohibits a state court from using any “legal or equitable” means whatever from forcing such a dispossession of the veteran’s benefits, and applies to all such benefits “due or to become due” and “before or after receipt”, and that same state court already ruled that 38 U.S.C. § 5301 applied to the very agreement at issue in this case?