ORIGINAL: jester_s1
There is no excuse for even starting a plane without having soloed with a trainer. It's against AMA regs (therefore illegal), it's not covered by AMA insurance, and it's dangerous and stupid. A person who would do that isn't welcome to fly near me and shouldn't be in the hobby.
Would you fly a model without the engine broken in and thereafter tuned properly? I don't know of ANY beginners who come into the hobby with a test stand and therefore the only way to break in the engine is by running it on the model. Teathered or well held, certainly, but there's one good excuse. When I was working with the flight school at our club we would have the students start their models (with a buddy) to get them used to it while the instructors were busy with the in-the-air students. Mostly because the "floating" assistants would spot problems during the pre-flight & warm-up well before the model was up in the "batter's box" for a flight.
The AMA is a wonderful organization but is not part of the federal or any state legislature or judicial branch and therefore cannot pass laws. Breaking AMA recommendations is not illegal. It is grounds for dismissal from AMA and most r/c clubs, but there again, no one is legally or otherwise obligated to be a member and their guidelines do not apply to non-members. It's not illegal to buy and turn on a transmitter even if it might interfere with other pilots. Just poor form.