[Fogest]

I don't see how the argument is much different than for someone having some beers? If they have a few beers daily and blow over is this fair as it likely is not impairing them due to a higher tolerance? How is this different than if a regular weed user were to blow over, but also may have a higher tolerance?

The problem is that you can't really test for these tolerances, especially not in the field. That's why it's usually better to air on the side of caution and set a limit.