It's not for the courts to decide. If it were, there would be a court-based requirement in the amendment. There is not.
It is a disqualification from office, just as being under the age of 35 is a disqualification from the office of president. No court ruling is required.
Edit: Other people who agree with me:
J. Michael Luttig, conservative former judge of the US Court of Appeals, Fourth Circuit
Laurence Tribe, legal scholar and professor emeritus at Harvard
William Baude, legal scholar and professor of law at University of Chicago Law School, Federalist Society
Micahel Stokes Paulsen, Distinguished university chair and professor of law at University of St. Thomas, Federalist Society