I know that in Texas, there is no law for or against it. This was according to the Texas State Trooper who taught my MSF course. It is that way in many states, i.e. - no laws specifically for or against it. The reason you see it occur more in CA is because it is more socially accepted in that state. It may not be a good idea to do it much in TX because ******* Bubba may not think it's right or fair and may take offense to it (which could be lethal to the smaller vehicle).
With that being said, you can be ticketed for reckless driving. That may be warranted or not, and could depend in large part on whether the ticketing officer is also a motorcyclist. There are still a lot of officers that don't have a full knowledge of traffic laws in their jurisdiction, especially when it comes to something uncommon like use of headlight modulators on motorcycles.
