I have been present when the RC was compelled by a competitor to file protest on a sailor wearing a CE vest. The RC thought they had it covered by making that rule non-protestable by a competitor. They didn't. The RC protested within the time limit on the last day and it was upheld. Because the SIs indicated that the penalty could be something other than a DSQ, the sailor received a percentage penalty that robbed her of the 1st place position at the regatta, rewarding the sailor who made the issue who had been in 2nd.

Like Karl said, you have to accept the possible outcome if you choose to break a rule. I wear a Zhik PFD to all events except the Alter Cup. I know what I could be in for. I'm pretty sure that the Alter Cup is the only event where people will do just about anything, including protesting a PFD to win.