Towey said:Simple answer. Sigil yes, Faerun only in smoke powder form, and nothing even resembling a firearm is permitted on Greyhawk even in appearance. All of this however is speculative based off of the various setting restrictions up there and my ideas/information on them.
A better solution than that would be a crossbow that fires bolts of spell storing. Still stat friendly and it provides for a bit of air of mystery if not chaos. Not only that but friendly on all settings that magic works.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.