Each guild is entitled to impose and enforce restrictions on the
products of its members' skills. However, the enforcement of such a
restriction may only be applied to members of that guild or other groups
under contractual obligation to heed the restriction. In other words,
you can punish a guildmember for selling a restricted product but you
cannot punish whomever bought it unless they or an organization to which
they belong has vowed to honor the restriction.

Guilds control supply; they do not control demand. If a guild wishes to
maintain control over a product of its skillsets, then that guild should
exercise careful screening and indoctrination of its novices.

It should also be noted that sufficient demand will always create
supply. If a ban proves so restrictive that supply of extremely
high-demand products dries up completely, alternate supply sources will
inevitably be created (I refer you to Seasone the Industrious as an
example). Therefore, it is in a guild's best interest long-term to
restrict the supply of only as few products as they deem absolutely
necessary.

-Varian

Penned by my hand on the 22nd of Chakros, in the year 54 MA.