Very simple, upon equipping the item you need to check the item ID range and see if its between a tails ID range if so, not allow it.
If your source is coded well it would be much more simple, in my first source from scratch it would've been like so:
Code:
if (item.isTails())
{
client.Send(New message("You are not allow to wear that **** bro, you crazy?!", Color. Blue, MessageID.Center));
}
^- three lines, job done.
#edit
incase you ask, IsTails is a method that returns a bool, it simply checks one of the current items ENUMS and tells you if its a tails or w/e, quicker then checking the ranges.