The RCMP’s ban on Ruger 10/22 magazines capable of holding more than 10 cartridges is unconstitutional, the lawyer for the Canadian Shooting Sports Association said, urging owners, importers and sellers of the products to join a legal defence.

Canada’s national police said in a statement on its website that the .22 Long Rifle magazines “are prohibited devices if they are capable of containing more than 10 cartridges,” reversing an earlier decision and threatening potentially hundreds of thousands of owners with criminal charges. Calibre Magazine wrote about the plan on July 18.

“The purpose of the action is to seek a judgement that these magazines are not prohibited, to declare the magazine-capacity restrictions void as unconstitutional or in the alternative to force a buy-back of each at full retail value,” Edward Burlew, the lawyer for the Canadian Shooting Sports Association, said today in a statement on the organization’s website.

The RCMP said it’s banning the magazines because they are designed for handguns on the Ruger 10/22 platform, as well as for rifles. Canadian regulations prohibit handgun magazines capable of holding more than 10 rounds.

The Canadian Sporting Arms and Ammunition Association, an industry group, said it is working with the Canadian Shooting Sports Association on the planned legal defence. There is no fee to join the defence, but the groups are asking for donations.

“This is one of the most common rifles found in Canada,” Rod Giltaca, president of the Canadian Coalition for Firearm Rights, said in a statement earlier today. He estimated there could be a million of the magazines in circulation in the country.

Canada has more than 2 million men and women licensed to own firearms.