Yes, it happened at last. The Justice Department is filing suit against a State in the union, because that state (which did not vote for the sitting President) passed an immigration law that directly undermines the authority of the federal government as enshrined in the US Constitution.

President Obama versus the State of Arizona? Nope. President Bush versus the State of Illinois!

The Bush administration took the gloves off Monday in its fight over immigration enforcement, suing the state of Illinois for banning use of a federal system that checks whether workers are in the United States legally.

The United States of America vs. the State of Illinois is the latest court battle the administration is waging with immigrant advocates and business groups over its crackdown on workers here illegally and the companies that hire them.

Brought by the Justice Department on behalf of the Department of Homeland Security, the civil suit is intended to preempt an Illinois state law that bars businesses from using the employee verification program until its databases are faster and more accurate. The suit is also intended to send a clear message to other states and cities about the way they handle immigration enforcement.

The Illinois law “is a direct assault on the federal law,” Homeland Security Secretary Michael Chertoff said Monday in an interview with the Los Angeles Times. “This is about as bold an anti-enforcement measure as I’ve ever seen.”

In both cases, then and now, the federal government is right to act against an errant state. Whether that state is red or blue, whether it passes restrictions on immigration or loosens them, a state may not dictate immigration policy. Ilegal immigrants immigrate to the United States as a nation, not a specific state, and the states cannot be permitted to enact a patchwork of law. This is a Homeland Security issue as well as a constitutional one and President Obama, and President Bush, are and were right.

Arizona and Illinois may be frustrated, but it is not their call. States’ rights advocates who invoke the Constitution must either accept this or be revealed as stunning hypocrites.