The time for the courts to review Obama's eligibility would have been before the election.
Now that he is POTUS, "upholding the Constitution" means impeachment.
I don’t have a problem with impeachment. Obama has most likely committed criminal fraud over his eligibiity. A court finding would help expedite the matter.
Now that he is POTUS upholding the 20th Amendment of the Constitution means the courts should declare that Joe Biden should have the presidential powers and Congress should be deciding what to do with Obama, who is a president with the Constitutional “inability to discharge the powers and duties of the” presidency.
That's just it...
Impeachment is for sitting presidents, and if one is not legitimately a president, there can be no impeachment.