It will depend on the national aviation authority. Sounds like in Canada they wrote it into the law. In the UK, it goes through the following stages:
They write the rules to ban it; (see the ANO)
They then employ a number of admin wallahs to receive all the requests for exemption. The operator/pilot have to engage in paperwork to get the aircraft and pilot approved, as well as writing an SOP that gets attached to the ops manual.
Once the weight of paper created exceeds the mass of those leaving the aircraft it is all OK.