On what basis to appeal. This is a complete blanket ban. The Supreme Court has already decided that the regulations about possession and use of firearms are within federal authority so there really is no need to consult on this. The only things that might be appealed are lack of compensation, or insufficient compensation but even that is a stretch.
I would note the governments true ideological intention was expressly stated by Bill Blair this morning - to end the “militarization in society” - to the extent that even actually exists in Canada. Note also they state in the Gazette that they have no idea of the true numbers of the “ implicated” firearms, but they also write with some glee that it will be “aggressive” males primarily located in Ontario, BC and Alberta who will be impacted. So no hit to the liberal voter base and that is the only thing that matters to these people.