- A sitting president of the U.S. sues somebody for something (what doesn't really matter).
- The defendant makes a motion for a subpoena/deposition/whatever.
- The President objects on grounds of presidential immunity.
- The judge upholds that immunity.
What happens? Does the judge tell the president to either waive that immunity or drop the lawsuit? Does the judge let the lawsuit go on, but grant the defendant the same immunity for the sake of fairness? Or what?