An Arizona Republican congresswoman named Martha McSally is running for the U.S. Senate in November, and she has a bold idea that may or may not become part of her official campaign platform. As part of a roundtable discussion on sanctuary cities at the White House on Tuesday, McSally made the extraordinary comment that the border wall between the U.S. and Mexico may not be the only one required to keep illegal immigrants at bay.

“As we look in Arizona, we often look into the dangers of the southern border,” McSally said. “But if these dangerous policies continue out of California, we might need to build a wall between California and Arizona as well to keep these dangerous criminals out of our state.”

Obviously, McSally meant this as a hyperbolic way to prove her point – that sanctuary cities aimed at illegal immigrants would drive more Mexicans to cross over, and eventually that influx would spill over into California’s neighboring states. But the father California strays from the foundations that keep our society tied together – the rule of law that transforms a piece of land into a country – the more this seems like a halfway reasonable idea. Because she’s absolutely right about one thing: What starts in California will not, by any means, remain in California. There’s only so much room, there’s only so much economic opportunity, and there’s only so much welfare flowing out of Sacramento.

Since the election, some liberals have tried to treat what California has been doing as akin to Texas and other conservative states battling Obama in court. It isn’t. Texas and a coalition of states filed suit against Obama because of an executive order (DAPA) that he wrote himself in defiance of existing U.S. law. If you want to make a comparison to California suing the Trump administration over the travel ban, you would be back to apples and apples. But on this subject – the subject of sanctuary laws – California is not challenging an executive order or some kind of White House edict. They are challenging congressional law. In other words, THE law.

Yes, there is a tried and true, legally defensible concept of “states’ rights,” but that only takes you so far. At the end of the day, federal law reigns supreme. California can perhaps get away with refusing to ENFORCE that law, but they cannot get away with actively THWARTING it. That’s as good as secession. Which would exclude California from the U.S. and make them a country unto themselves.

So while it may sound ridiculous to start talking about building a wall between Arizona and California, it is a species of ridiculous that may seem less so after a few years. Ultimately, it may come to seem quite necessary.