Ideally, but the Courts are starting to look more and more political. Would you trust a Court with a majority of GOP appointees to adjudicate whether an action by a GOP president exceeded the authority of his office? I wouldn't.
I think the more we place procedural limits on what presidents can do, the more we protect ourselves from the president becoming a de facto potentate. We came so close to that after 9/11, with an executive which did not recognize any rightful limits on its actions, a cowardly legislature terrified to appear "soft on terror," and a highly compliant Court system. The more we can hem in the president with explicit limits, the better, since all presidents always lean towards self-justification of any action not explicitly prohibited in law.
Whether you think the biggest threats of dictatorship come from the right or the left, the threats do come, periodically, and public opinion is no protection of liberty in times of danger, real or imagined. Because our system is adversarial, limits on a particular office will only ever be introduced by the opposing party, and the motives will always include the most cynical and crass partisanship. That in itself does not invalidate an action -- for example, the impeachment of Nixon would have been primarily driven by Democratic members, and it would have been in part partisan, but it would still have had other valid reasons. The lawsuit against Obama doesn't stand up to that test -- it's just rage-inducement to get feet to the polls (and in that regard it may backfire).
Until Congress is willing to act responsibly, the executive will continue to be given a long leash, since his expansive powers are so useful to Congress as an excuse to pass the hot potato.