I think the best heckle I had while riding my unicycle was from a policeman who shouted "Are your brakes working?"
(In the UK you are required by law to have working brakes on a bicycle. My unicycle had no brakes at all! Though slowing down was never a problem with the fixed wheel drive.)
In Germany a fixed wheel does not count as a brake, and passionate fixie drivers will have a rear brake installed but never use it.
The signs on the rim of a brake that has been used is frowned upon by o̶b̶s̶e̶s̶s̶e̶d̶ passionate fixie drivers.
Sounds like the rules are the same actually
In the UK a bike is required to have 2 brakes, and a fixed wheel counts a single brake, i.e. you can't ride a fixie with no extra brake but you can with a single brake
A fixed wheel counts as a brake, though I've only seen the law in relation to bicycles which require 2 working brakes not sure how this applied to unicycles.