Helmets in the US aren't "certified" by anyone. The manufacturer places the DOT sticker on them signifying that they meet FMVSS 218. DOT doesn't do any of the testing either, the manufacturer does. The only independent tester is Snell, but a snell cert doesn't make it legal either. IMO the euro standard is much better, but not recognized in the US probably because there isn't enough beaurocracy and the politicians don't get paid off by the EU.
If you like a euro helmet without a DOT sticker, add one and wear it. It's your call.
I have this one on my beanie. Had it for 15 years, many thousands of miles in many states, never pulled over.
If it's a big helmet that's at least 1" thick you won't have any problems anywhere in the US. The law is completely unenforcable anyway.
