There is one thing that cannot be enforced by law. COMMON SENSE! Which brings me to PFD usage.
I grew up on the water and as a kid I can never remember wearing a PFD except when it was real stormy or I was water skiing (BTW I remember when we all got mad when the USCG didnt approve ski belts) There was no discussion of proper usage in our household only that the USCG required them.
When I was a teenager and was introduced to cat sailing nobody wore one, yes they were on board usually tied to a boom or hiking strap. When we capsized or got separated from the boat we swam to it, righted, and took off again. Not once did we say: "You know it might be a good idea to put these on!"
Fast forward to 1991. I buy a cat after after some 7 years hiatus from sailing. Our first ride with my wife I did what I remembered we always done. I tied the PFD's to the hiking strap. Trying to get back to shore during a t-storm that day the hiking strap came loose during a jibe and there went my PFD's. No way was I going to go back and retrieve them! But it was the scariest ride to the beach I ever had!
That's when common sense crapped on my head! What the hell was I thinking? What if my wife fell overboard? Would I be good enough to sail back to her? What if god forbid I fell off?
She doesn't know how to sail! We are good swimmers but not that good! It was a moment of clarity. I was an idiot! If my wife was to die of my lack of common sense I think I would kill myself. If I was to die it would be devastating to her. We made it back OK. I vowed never to leave the beach without my PFD ON ME AND MY CREW!
Two months later while sailing in high winds I fell off. My crew capsized trying to get back to me. I couldn't swim to him, damn that boat is fast on its side! I had my PFD on and thank god. It took 3 hours before helped arrived and plucked me from the water. While floating for three hours in 3 foot chop I wasnt worried. I was calm and peaceful, I knew help would eventually arrive. I didnt have to worry about, "Can I swim to shore?","How much longer can I tread water?" All the griping I did about how uncomfortable they are, decreased mobility, etc. etc. seemed very stupid while I was floating by myself. You will never hear me bitch about PFD's again.
Which brings me to the mandatory PFD usage. While I still see quite a number of sailors still wearing nothing I don't think a law will help. It is going to take a moment of common sense to rain on them and give them some clarity. I just hope they get lucky when it happens like I did.
Or hopefully a mild horror story will help :-)

JDR