The joke's on them, of course, because Cap no longer has Iron Man's highly advanced 1960s transistor-powered magnetic gimcracks inside his shield, and he proceeds to beat the living hell out of the convicts. Then he frees the warden and asks what was that all about?
Who thought this was a good idea? That yard would have dozens of criminals who were put there by Captain America. Heck, since he went into the iceberg twenty years earlier, there were probably some convicts still serving their term from then. The warden's choice of code words was not the most prudent, he should haved used "Euripides" or "Machiavelli," someone like that.