Sorry, thought about it at the time but didn't write it - they are actual bicycle helmets styled like skateboard helmets. They're fully rated for bike riding.
If the cops stop you (which they do, occasionally) and you are actually wearing a skate helmet, not rated for bike riding, that doesn't count as 'wearing a helmet' and you'll be fined.
(I'm sure the idea of being fined for wearing the wrong helmet will horrify some people but remember, that's the law here. The law also says you need a bell on your bike. It's rare, but the bike police do random stops and if you don't have a bell, strictly speaking, you'll be fined. Never happened to me, but it can.)
((Which, by the way - and sorry for the errata with the double-brackets - I actually support. I ride through central Melbourne. Pedestrians are a nightmare. Having a working bell is actually important. They cost $5. The law is a public service which, in this case, works. Get a bell.))
