In the UK, anyone who is aged 14 or over and wants to ride a battery-powered bicycle can do so – they don’t need tax, insurance or a license. But in Northern Ireland the same bike and rider must have tax, insurance and license

Despite only having small motors and generally only being capable of speeds of around 15mph, the bikes are still legally classed as powered two-wheelers and in the same classification as mopeds.

Throughout the rest of the UK, legislation was passed in 1995 that ruled the Electrical Assisted Pedal Bicycles – or EAPCs – exempt from that ‘moped equivalent’ law, but it’s come to light that Northern Ireland didn’t implement the same exemption.

So far, they aren't wasting time ticketing the very, very few people that might be in violation... but it's on the books

http://www.motofire.com/2017/08/news/northern-irish-electric-bicycle-riders-need-motorcycle-licenses/