No doubt, there’s a clause buried deep within the software use license that essentially says “we can take this away from you at any time for any reason or no reason”.
To refresh my memory, I just reviewed their MASTER SUBSCRIPTION AGREEMENT and there is nothing there that limits what customers can sell on the SFDC platform.
HOWEVER, I just reviewed their Acceptable Use and External-Facing Services Policy which was last updated April 11, 2019 and found this:
Worldwide, customers may not use a Service to transact online sales of any of the following firearms and/or related accessories to private citizens. Firearms: automatic firearms; semi-automatic firearms that have the capacity to accept a detachable magazine and any of the following: thumbhole stock, folding or telescoping stock, grenade launcher or flare launcher, flash or sound suppressor, forward pistol grip, pistol grip (in the case of a rifle) or second pistol grip (in the case of a pistol), barrel shroud; semi-automatic firearms with a fixed magazine that can accept more than 10 rounds; ghost guns; 3D printed guns; firearms without serial numbers; .50 BMG rifles; firearms that use .50 BMG ammunition. Firearm Parts: magazines capable of accepting more than 10 rounds; flash or sound suppressors; multi-burst trigger devices; grenade or rocket launchers; 80% or unfinished lower receivers; blueprints for ghost guns; blueprints for 3D printed guns; barrel shrouds; thumbhole stocks; threaded barrels capable of accepting a flash suppressor or sound suppressor.