This strange alliance has developed in response to one of Congress’s rare bipartisan achievements—the 2012 National Defense Authorization Act (NDAA). That bill affirmed the long-standing distinction between civilian justice and the rules of war by letting the President detain terrorists (including U.S. citizens) captured anywhere and question them as long as necessary. A President can decide to try them in either military or civilian courts, and the right of habeas corpus to challenge detention in court, established by the Supreme Court’s 2004 Hamdi decision, is unchanged.

This modest law has sprouted a burst of political delusion in several states and Congress. A tea party outfit called the Tenth Amendment Center calls the law “an unconstitutional and dangerous federal power grab”—though the statute merely codifies existing practice under Presidents Bush and Obama. In the wilder tea party precincts, the talk is that in a second term Mr. Obama might round people up, a la Japanese-Americans after Pearl Harbor.

The paranoia is showing up in state legislatures, and this month Virginia became the first to forbid state employees from “assisting” the feds “in the conduct of the investigation, prosecution, or detention of any citizen” under the provisions of the NDAA. This means that as of July 1 in Richmond a state trooper could not arrest the likes of the late Virginia cleric-turned-terrorist-recruiter Anwar al-Awlaki because he might end up in a military brig. A U.S. missile targeted and killed Awlaki in Yemen on Presidential orders, but Virginia police couldn’t detain him.