Okay, here we go. I may have mentioned this before, but I feel I must mention it again. As recently said to me by the Task force RSM "you can say anything to anyone, it's all HOW you say it that matters".
Dress regulations and enforcement are the responsability of everyone. If you see someone out of dress, tactfully correct them and you should have no issues. MAKE SURE YOU ARE CORRECT FIRST. For instance, I once saw the base commander at Timmies with a huge thread stuck to his beret, I kindly informed him that he had one and offered to remove it for him, he thanked me and carried on his way. Why did I say anything? Because he represents the CF in his uniform and the way people (civvies) look at him affects the way they look at all of us, same goes for the guy walking the dog.
Stop your bike, approach the gentleman and suggest that maybe he forgot to put his beret on inadvertently when he left his house?
I don't know, the other technique would be do quickly remove and identifying factors on yourself and do a drive by correcting... "Put your darn beret on!!!!" That usually spooks em enough to do something as they aren't sure what rank level yelled at em.. hehe
Good luck, if you get in trouble.. you don't know me.....