If France did not restrict guns, this would surely happen much more often.
Why would it not happen much less often?
Giving an ordinary person a firearm doesn't change him into something he isn't already.
This guy was not a particularly capable terrorist , but he was able to arm himself .
If the bad guys get guns in spite of the rules , and the good guys obey the rules , then the bad guys will be armed and the good guys not .
I think this is a good description of this particular situation.
Doesn't it also describe the more general situation?