Presidents are effectively immune to the consequences of most unconstitutional actions. This could be settled definitively however that isn't really wanted by the majority of those who have the authority to act or their supporters.
If the War Powers Act is being violated then Obama can be impeached. It would be difficult to imagine a defense that would not involve the WPA. That would force a decision by the SCOTUS which ought to resolve the issue.
Impeachment over violation of the WPA has nothing to do with forcing the Supreme Court to do something. When it comes to impeachment Congress is the only judge.
