Well, that precedent was set a long time ago. Before 1996, when the problem was fixed by federal source tax legislation, California forced anyone receiving a pension from a California entity to pay income taxes in California. Period. It didn't matter where you lived.
I'm not sure about the nuts and bolts of enforcement but there was a time that if you worked a long career in California as a teacher or state government employee, retired, and drew a pension, you still had to pay California income taxes no matter where you moved. While that has been changed for over 20 years (if you earn a California pension, it's only taxable under the widely-varying laws of the states of residence) it was once a thing. Some sort of outside-the-state auditing capability had to be built into that system.
I feel quite sure many state government taxing authorities would be quite willing to find a way to rebuild the bureaucracy needed to conduct audits all over the rest of the U.S.
Hey, just because you live in Lyon doesn't mean you can't get called into the Paris consulate for the IRS to audit your taxes. Why should states feel they should have any less reach?
In practice, IRS audits of expats are almost exclusively done via correspondence but, while highly improbable, it's still possible to have a Revenue Agent or Officer knock on your door anywhere in the world. (In fact, the Paris posting is one of the most sought-after positions in the bureau.) Where the states are concerned, I don't expect that California will set up a tax office in every major city in the U.S. but I can easily imagine some sort of correspondence audit system coming quickly into use. Eventually, I'd envision states cooperating and performing audits for each other.
ETA - Yes, I understand that this thread isn't about income taxes but when it comes to enforcement mindsets, all taxes can be discussed collectively.
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