Let’s take the situation of the town of Paisley (see below).  It can’t prevent other people from producing paisley patterns because the patterns are in the public domain, and it can’t keep them from describing the patterns as paisley, because the term is now descriptive.  What it might consider in order to recapture some equity from having developed the paisley pattern, is to develop a new certification trademark for goods originating in Paisley, and attempt to teach the public that paisleys from Paisleys are better.  As a model for that, take a look at the new certification mark from Venice depicting its winged lion (above), described in this article (in Italian) and this article, in AP newswire.