If it gets to the Supreme Court and the Court does rule that the executive can exercise discretion in the enforcement of law you will have the option of enforcing it or not enforcing it at your discretion. California passed a law making medical marijuana legal under state law, but it was still illegal under Federal law, the Feds started arresting and closing down the purveyors, Attorney General Holder unilaterally decided not to enforce the Federal law, does he have that right or is he bound to enforce all Federal laws? If the Court rules that he has the right to exercise discretion in his enforcement of Federal laws, every jurisdiction in the United States is governed by precedents established by the United States Supreme Court and all jurisdiction will have the right to exercise discretion in their enforcement of all laws. If the case only gets as far as a Federal District Court or the DC Court of Appeals and either or both of them rules for the President their decisions will not be binding upon a local AHJ, for a Federal decision to set a precedent for an AHJ in Southern California the decision would have to come from the District Court for the Southern District of California, the 9th Circuit Court of Appeals, or the U.S. Supreme Court. Obviously that's not going to happen in the lower courts since Congress will be filing the case in Washington, so it will only apply to you if the Supreme Court takes it, Congress may even ask the Supreme Court for an expedited hearing like they did in Bush vs. Gore this issue is so large and affects the entire nation.