Sure it's known and one of the primary battlegrounds in court challenges. The Supremes have, so far, ducked the issue and only addressed it secondarily. The Supreme Court is under no obligation to hear every case which is referred to it. They pick and choose what cases they will hear for any given term. SCOTUS has very few specific things they must do under the constitution. They are free to ignore nearly everything short of cases involving disputes between states, handling cases against foreign ambassadors, and forcing the Chief Justice to preside over Senate impeachment trials against the president (Oddly enough, in all other impeachment trials, the Vice-President presides even if it's his own impeachment trial! Now you know why Cheney wasn't impeached.).