Why not refuse to sell them?

[Nuclear Unicorn]

5. Semi-automatic long guns are one of, if not the, most popular rifles for hunting and competition.

I've read elsewhere this is partly due to the "Streisand Effect" the phenomenon where by seeking to obscure a thing the thing gains in notoriety and popularity. What I read claims the original "Assault Weapons" Ban made people look twice at the rifles and once they began handling them the platform's popularity exploded amongst hunters and competitive shooters.