The judicial branch can decide that a law is not constitutional. It's then Congress' job to find the political will to make the law constitutional. Either by altering it, or amending the constitution. It's a governor on the system. Only the important stuff is supposed to make it past all three branches unscathed.

It either has to be something populist - everyone wants it so I won't get voted out of office - or it needs to be worth spending a ton of political power. When Congress is overwhelmingly in favor of a law, they can prevent a presidential veto. But that degree of unanimity is rarely free. It cost people something else, so it better be worth the opportunity cost.