Most convincing is the argument that Obama has the right to do this because, after all, the executive branch gets to set enforcement priorities. And yes . . . but no. At the point at which you are announcing that the law won’t be enforced against a large fraction of the people who are violating it, then you are effectively rewriting that law. Few of the people who are coming up with these justifications would sit quietly while a Republican president, say, announced that he was ending audits and OSHA inspections for small-business owners so that he could refocus resources on earned income tax credit fraud. And if you wouldn’t view that as an acceptable use of the president’s power, then you should not endorse this power grab, either. Immigration is an important issue, one on which I would like to see significant changes in policy. But the rule of law is an even more important one.

The last 15 years have witnessed far too many presidential assertions of unconstitutional authority — and too many members of both parties who were willing to endorse those extralegal actions as long as it was their guy bending the rules. The result is a constant ratchet toward an imperial presidency.