The court ruled that the separation of powers does not mandate that the federal court delay private civil lawsuits against the president until the end of their term.
The court ruled that they didn't need to decide if the petitioner's assertation of immunity may succeed in state court, and use federalism and comity concerns instead of the separation-of-powers argument.
The court notes that the decision rejecting immunity and allowing the case to continue does not require them to answer the question of whether a court may compel the attendance of the president at any certain place or time.
Breyer argued that presidential immunity would apply if the President could prove that a private civil lawsuit would somehow interfere with the President's assigned constitutional duties.