Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

So? It'd be the law. It will deter a lot of people from cycling. We've seen that in other countries.

What grounds do you have to believe that it won't be brought in, followed or successfully enforced? No law (I guess) is enforced 100%, but why should that somehow absolve us from action now?

Don't get me wrong. I don't want to see it brought in and I see the negative effects of it being brought in, but I don't agree on me signing the petition.
I am just speculating that I cannot see a way of enforcing a helmet law when places like London have schemes set up to promote cycling so much. I have no evidence, I just see a lot of more against arguments for it than pro and too many complications for it to work.