(KE, our resident legal scholar): By your method,
the FAA will regulate models by being forbidden by Federal Law from regulating models???
If section 336 simply said "the FAA cannot regulate models" you would be right. It doesn't, so you're wrong. Nobody here wants the FAA to impose stringent limits on models within five miles of an airport, and I don't think any of us thinks it's likely that they will. But if they get a notion into their heads that they ought to, there's plenty of slop in the language of section 336 that would let them do it, your views on statutory interpretation to the contrary notwithstanding.
There's a fundamental difference in the way lay people and lawyers look at legislation. Lay people ask "what is the obvious meaning of this language?" That's the way most of us use language most of the time. Lawyers ask, "What are the possible meanings that could be given to this language?" There's almost never a simple one-line answer to that question. And while it is indeed absurd to talk about the "intent" of people who haven't even read the thing, courts and administrative agencies do it all the time. If the FAA has its heart set on regulating us, there are plenty of ways for them to do it. To find them, you have to read the whole statute carefully, not pluck a few words and phrases out of it and yell "Gotcha!"
You might take a look at the thread about the guy flying from a church parking lot near the landing pattern of a controlled airport. So far, not one hint in any of the posts there to suggest that he couldn't, or shouldn't, be stopped. And the new law won't change that one bit.