Can't be an EU law, few things are outside of the very specific scope of product feature requirements. Germany (part of the EU) has or exactly reverse: explicitly posted speed limits apply to bikes just like they do to powered vehicles, but the law that defines the implicit speed limits (50 inside cities, 100 outside) is written with wording that explicitly restricts its applicability to powered vehicles (that's how the superset of motorcycles, cars and trucks is usually written). This certainly wasn't the intention of that law, but it has been tested in court. When you use that loophole, "they" can't do anything about it other than invoking the catchall law of "don't do unreasonably irresponsible shit in traffic" (which certainly they can)