Why Alito should not be a Supreme Court judge
"Of course the President has to follow the law."
"So long as it's constitutional."
Like most talking points, this sounds almost reasonable, but as with all talking points, it's that last little detail that makes it nuts: so long as it's constitutional. Who decides if it's constitutional? That's the job of the judiciary, right?
What the talking point says is that it is the job of the President to decide whether a law is constitutional until the courts explicitly tell him the opposite. In a limited sense this is often necessary, I'm sure: staff lawyers in every department have to decide if given actions violate the law or the Constitution, and the question isn't always clear-cut. But it is not supposed to be the main purpose of the Executive Branch:
The administration of government, in its largest sense, comprehends all the operations of the body politic, whether legislative, executive, or judiciary; but in its most usual, and perhaps its most precise signification it is limited to executive details, and falls peculiarly within the province of the executive department. The actual conduct of foreign negotiations, the preparatory plans of finance, the application and disbursement of the public moneys in conformity to the general appropriations of the legislature, the arrangement of the army and navy, the directions of the operations of war, these, and other matters of a like nature, constitute what seems to be most properly understood by the administration of government. [Hamilton: Federalist 72]
When a President does disagree with a law, he has the power to veto it. What he is not supposed to do is sign the law and then declare he plans not to follow its obvious meaning. He is not supposed to evade laws that explicitly require warrants for domestic wiretapping and then make excuses about why he never sought to have those laws changes.
The Constitution's main mechanism for controlling an out-of-control President is our system of checks and balances. That means the legislative and judicial branches have to assert their powers. Even under the most generous definition, that cannot possibly include the confirmation by the legislative branch of a Supreme Court nominee who believes a President can do whatever he wants.