Actually, while a helmet is definitely, a good idea,
the principle that the government can require
that one be worn, is an unwarranted infringement
on the riders freedom.
There are proven cases where a helmet has caused an accident
(by restricting peripheral vision eg.).
It should be the riders choice.
That said, that turban of the Sikh's offers about as much
protection as a helmet.
There's a lot of padding there, and being twined in his hair,
it's fastened in place.