This was not a self defense case, it was a safe storage case, and it turned on the insanely poor and ambiguous wording in the act.
For years there have been long threads on gun forums of people, including lawyers, debating the meaning of that section. It is that unclear. There is a lot of other poor and ambiguous wording in the act as well.
I don't have any problem with the general idea of the safe storage law, but it needs to be rewritten to make it clear and simple.
Considering it is a criminal charge if you get it even slightly wrong firearms owners need clarity on what the law expects of them.
There is another issue here which is aggressive prosecution. The Ontario crown is flat out hostile to gun owners and takes almost any opportunity to lay a careless transport or storage law, taking advantage of the ambiguity. Then they try and plea deal down to a weapons prohibition. Most don't want to risk a criminal record or a lengthy trial as this guy did and wind up losing their guns.
The hostility towards law abiding owners using criminal law is really pretty offensive.