The only regulations the FAA may be able to apply are the regulations for obstructing airspace. IE don't fly in front of planes. Part 91 specifically says that it applies to all on board the aircraft so it does not apply. Also in the Pirker case the NTSB judge said there are no regulations that apply to model aircraft. I know the FAA is saying otherwise, but saying so and actually charging you for violation of a regulation are two different things.