Originally the 550 was prohibited because it was on the ATF list of prohibited rifles that couldn't be imported into America.
The 550 didn't even start to be exported to America at that time and they were coming into Canada.
So, the RCMP used the ATF list as a template for the Justice Department prohibited list
The ATF list was just to stop the importation of foreign made guns, to keep the manufacturer's happy
Then the importers in Canada started fighting over 550's and got them banned, then the 550 Swiss Rifle colour series got caught up in additional issues
None of which served the Swiss rifle owner's who just wanted a nice non restricted n range rifle to replace the target model AR15 Rifle which is restricted