President Obama is threatening to veto a law that would allowCongress to sue him in federal courts for arbitrarily changing or refusing to enforce federal laws because it “violates the separation of powers” by encroaching on his presidential authority.“The power the bill purports to assign to Congress to sue the President over whether he has properly discharged his constitutional obligation to take care that the laws be faithfully executed exceeds constitutional limitations,” the White House Office of Management and Budget said Wednesday in a statement of administration policy. “Congress may not assign such power to itself, nor may it assign...