In the past, people who attempted to sell pinholes have left themselves open to this kind of attack by claiming that pinholes can permanently eliminate all kinds of visual problems. Such claims could not be substantiated. The recent case where a lawsuit was brought against the tobacco companies is one of the few instances. That might be understandable since tobacco is an extremely harmful product that was costing the states hundreds of millions of dollars in health care costs. But pinhole glasses are a perfectly harmless device, even if exaggerated claims were being made.
Exaggerated claims seem to be the rule in the marketing world.
We are certain that if there was a way to make squinting illegal, they would try to do it. The reason is that any attempt to mass distribute them has been deliberately and massively squashed. Of course, it doesn't. For a shocking story on this topic, see Dangers of Fluoridating Drinking Water. Fortunately, the dictatorial powers of the FDA were considerably diminished by a recent landmark court decision.