Hi Caduceus,
It's not that CLH trailers in general are not approved, but specifically mine. I know of at least one other Dutch BC23 who had his trailer approved.
The reason for the approval process is that in The Netherlands we need a license plate which is tied to the trailer rather than the car. In order to obtain this license plate the trailer needs to be approved for road use. In my case CLH forgot to stamp the VIN (vehicle identification number) on the chassis. Without this VIN, the origin, year of build etc cannot be traced (it could even be stolen) and the approval grinds to a halt. I've been in contact with CLH several times. They promised to gather and send some information which just might help me to get it approved, but I haven't heard from them in weeks and I'm running out of time now and decided to purchase a new trailer.
There's no reason for concern when going abroad with your trailer.