I think this is on a con-by-con basis.

• Me and my cousin went to one that said “No solicitation signs. This includes signs offering physical contact…”
• At another con it just said “Prohibited Items … Signs of any kind.”
• I didn’t go to this one myself but my cuz went to one that said “Signs that promote any sort of solicitation are prohibited.”
• I coulda sworn that Pax East had a similar policy but I don’t see it now so maybe not.