In Norway they where actually forbidden until 2003.
I didn't know that.
Though, if there is no law regulating a vehicle, it's not legal I guess...
In my opinion, the regulations regarding power should be adjusted to each country's topology; there's no fun riding an e-bike in hilly Norway with just 250W, but in the flat Netherlands or Denmark it would be ok for assistance...
I myself @ 80kg with an 750W motor barely manages 25km/h up an steep hill... (Though, 40+km/h flat country are no problem (no pedlec, but with, it would be legal (except for the power...)).
I think there has been a change in the regulations regarding mopeds here; before the rules was max 50km/h, max 2.5hp, and now I think they've removed the 2.5hp limit, or adjusted it to 4-5hp?
That way, one can keep to the speed limit, and keep the speed uphills too...
(Edit:
My point with the last statement was that similar adjustments to the law should also be applied to e-bikes...
)