Here's a paper from 2011 that suggests such a law might have some effect, since apparently helmet laws reduce organ donations.
Here's a related news story that came up when I searched:
Economist studies link between helmet-free bikers, organ donors
I'll post market design related news and items about repugnant markets.See also my Game theory, experimental economics, and market design page. I have a new general-interest book on market design: Who Gets What--and Why The subtitle is "The new economics of matchmaking and market design."