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
We initially started this blog for our Market Design course. We'll post news stories (market design is everywhere) and other items (including stories related to repugnant markets). It is meant to supplement the course page, and Al's Game theory, experimental economics, and market design page.