Copyright Shield Designs ?

[madoc]

Here's a difficult one.

A re-enactment group takes a design from trajan's column, alters it and adds colours to make it unique. Someone now leaves that group and duplicates that design onto other shields for a new group.

I know plenty of re-enactment groups have split before and this sort of thing goes on all time, sometimes with fights over group names.

Is this really worth persuing under copyright on the shield design ?