First of, we'd really like you to wear a helmet since there are more benefits of doing so compared to cycling bare-headed. However, when it comes to enforcing of wearing a helmet by local laws, things get a bit more complicated.
Here's a map showing bike helmet laws by country:
As you can see, wearing a helmet when cycling is mandatory in Canada's British Columbia and Newfoundland and Labrador, Namibia, Australia and New Zealand. These are the places where you can actually get a ticket for not wearing a helmet. In a few other countries it's also mandatory, but without any fines in case of non-compliance.
What is more interesting, in the most bike-friendly countries like Denmark and Netherlands it's not even recommended, let alone mandatory. Why so? Because they have infrastructure in place which makes it safe to ride without helmets. Not only that, the motorists are used to nearby bicycles and any accidents are very rare. Here's how a typical street looks like there:
Did you notice someone wearing a helmet? Still, these are two safest countries in the world to ride a bicycle.
You see, many governments try to fix the problem of accidents involving cyclists by enforcing usage of helmets, instead of creating infrastructure for cyclists, and that, we think, is a major problem here. What is worrying, more and more cities see it as an ultimate way to fix the issue. Of course, it's cheaper compared to construction projects, separating traffic, educating motorists, etc. But is it a better way?
Enforcement of helmet use is often based on fear. You will see terrifying statistics of brain injuries, interviews with those who survived, etc. But, several new problems arise here.
First, people don't usually like to be told what to do. Secondly, fear is a great tool to make people do what you want them to. Let's take an average Joe trying to lose weight who considers cycling a new alternative way to commute to work. It's a hard decision for Joe, but he's almost ready to buy a bike. Next day, Joe's city council passes a bylaw, under which it's now mandatory to wear a helmet, or you're getting a heft fine. Joe now thinks, well, they wouldn't pass such a law unless there's a threat to me, right? So cycling is now perceived as something dangerous and less appealing. Joe goes back to his car.
When mandatory use of helmets was introduced in Australia, the number of cycling commuters has fallen significantly. As a result, with fewer bikes on the road, cycling is becoming more dangerous for those who still ride. Motorists are becoming less accustomed to their two-wheeling neighbours and accidents happen.
In addition to that, a number of studies show that drivers seeing a cyclist without a helmet are tending to pass him closer or perform a dangerous maneuver. On the opposite, when a cyclist has no helmet, passing motorists will be more careful, slow, and pass with a bigger gap.
This angle becomes even more fascinating when you look at a public health from this standpoint. It's a known fact that regular cycling helps prevent a number of diseases caused by inactive lifestyle. Now, if we compare a number of deaths caused by non-wearing a helmet and those deaths caused by non-cycling, the difference would be staggering.
What we think is the right approach, is enforcing helmet use by kids. First, because they can't decide by themselves, yet. Secondly, because kids tend to be less cautious than adults when it comes to cycling.