I suspect this is one of those cases where something that looks like a simple solution to a moral dilemma actually opens up a big can of worms. I believe the current way of thinking is that we don't have any say over who another country allows to serve in their military. So a citizen who is eligible to join a foreign military just has to jump through the expected bureacratic hoops at the Canadian end for a long stay abroad.

We'd either have to bar all foreign military service by Canadians (which will cause some dual citizens to lose their foreign citizenship through no fault of their own), or somehow put Israel in a special category, which I don't see happening.

It might be possible to have people who have served in the IDF arrested and tried for war crimes upon return to Canada, but it would require some work to make the charges stick.