"RST Engineering" wrote in message
.. .
Does anybody know if federal case law exists challenging state
registration of what the federal government already registers?

I'm not aware of any successful challenges. Every now and then, someone
claims that states have no right to require pilot registration, or aircraft
registration, or whatever, due to federal precedence. I haven't seen anyone
actually prove that, however.

I think they'd have a better chance doing it with pilot registration. The
aircraft registration, at least in WA, is basically a property tax. They do
exempt aircraft not flown in the state (and some other stuff), but I don't
think that's the same as requiring registration as a condition of operation.
After all, aircraft can be registered elsewhere and still flown in the
state. So it would be harder to assert that the state was trying to horn in
on the federal government's territory.

Even the pilot registration is debatable, since it's applied to state
residents, not to pilots generally.

Pete