There seems to be something happening in the EU over licensing of bikes that fall somewhere between light motorcycle and unregulated E-Bicycle. These are sometimes called S-Pedelecs. The Netherlands seem to be planning to treat them as mopeds (UK AM Licensing class) from 2017 and so require helmets, plates, insurance etc.
http://www.bmf.co.uk/news/show/mopeds-or-bicycles-what-helmet-law-applies-to-speed-pedelecs
I have no problem with 50cc mopeds and the equivalent electric powered devices (approx 30mph, 3.5Kw) requiring helmets, registration, MOTs, insurance and tests. I'm also happy with some of these to be less of a requirement than 125s and above. But please, let's keep bicycles unregulated including e-assist bicycles.
This is fairly clear for something that looks like a scooter or small motorcycle. The tricky bit is what we think should be done for things like the Stealth.
And of course then there's the whole issue of enforcement. I frequently see unregistered field bikes being ridden on the back roads round here. The kids are usually wearing boots, gloves and MX helmets so not completely stupid but still highly illegal. Does anyone care? At least if they were on electric field bikes, they'd be silent!
In the States its 500W . I think this is more fair as 20mph isn't that quick .
If it looks like a bicycle and is doing bicycle things, then nobody cares. but if you're doing 30mph on a thing that looks like a scooter with no helmet or plates, you'll get pulled.
Even with the UK-EU limits of 25kph, 250w, there's no real agreed testing procedure and the power is continuous, not peak. So you could have 1kW, 0-10mph, 250w 10mph to 18mph and be almost legal. Everybody seems to be relying on a maker's mark or plate that says "250w".
Then there's the confusion about throttles, the EU doesn't allow them, the UK did. So existing bikes are grandfathered in. Personally, I don't see the problem and would rather they were allowed as it makes riding in dense traffic easier.