Assume that the United States Supreme Court has previously determined that regulation of traffic on county roads is a power reserved exclusively to the states. In reaction to this opinion, the United States Congress enacts a statute providing that the regulation of county roads will be within the jurisdiction of the United States Congress from that date forward. Your law office represents a client who is charged with violating the federal statute that prohibits driving on all roads while intoxicated. Do you have a defense? If so, explain.