Well, it is not illegal. If you take a vehicle in for an inspection without an engine, they will take your money, but you will fail safety and emissions. If you take it 2 more places and fail, the state will fine you. Actually, you get investigated. Apparently, a bunch of failed emissions tests throws up a red flag, almost instantly.
If your vehicle has no engine, it fails many things, like steering, throttle, brakes, etc. 9 items fail, I believe.
Next time I take my truck in, I think I'll remove the power steering.