[ISL]

Agreed, unless the fixed number is zero.

You ban anyone selling banned items. I think vendors would respond quickly by self-censoring, especially the big guys.

Assisted-opening knives are a tiny fraction of Amazon's sales. If assisted-opening knife advertisements cut off Amazon's entire account, as has happened with Knife Depot, I'm pretty sure that Amazon would de-list assisted-opening knives.

A zero-tolerance policy, coupled with ample forgiveness for infractions, would be fair. Alternatively, you let anyone advertise anything.

Anything in-between turns Google into a kingmaker.

(NB - the very notion of censoring listings at all carries its own troubles, not at issue here)