Hi Laura
I agree with you that things get complicated partly because there are those competitors who either simply don't care to familiarise thmeselves with the rules, or knowingly 'push the barrier' to get an advantage.
I firmly believe that a hard line must be drawn, otherwise people will keep pushing that barier: - so i suggest the following:
1)Let people know in writing that if they break the costume code after a certain date they will be disqualified.
2)The judges are told to simply not mark those who break the costume code.

Those who are responsible for running competitive dancing must make sure that all competitors will in fact reasonably see new rules. This point is often skimped on.