You don't understand how FOPA works.  FOPA is not merely a procedural defense.  It is a due process protection against being arrested for mere firearm possession <i>by local authorities</i>.<p>In that situation, FOPA provides for automatic dismissal; the burden is on the local jurisdiction to prove that FOPA does not apply.<p>TSA stops are not arrests; the TSA is a federal agency, and so FOPA does not bar the TSA from detaining persons for firearm possession.