It's an excellent question.
The fact is there are individuals who, for whatever reason, and we don't understand why—are fortunate to have escaped the horrific adverse effects that other veterans and service members have experienced from this drug. Good for them. Thank goodness they haven't gone through what some service members have gone through. There are intelligent individuals, doctors and senior officers, who I think we can all agree have made a fully informed decision to take mefloquine. As I mentioned, the drug is licensed. It is approved by Health Canada for prevention of malaria, so there would have to be some sort of policy, and some very good reason, for that drug to be denied to service members.
I think a very strong case can be made that even if an individual states a preference for the use of mefloquine on deployment, and they have previously tolerated the drug—again, fortunately, for whatever reason—the residual risks to the military, and to that individual, from their subsequent use of mefloquine are simply too high to permit them to make that choice. A reasonable argument can be made for policy to restrict the use of that drug in operational settings.
I don't believe Canada has such a policy. At times, military organizations have implemented such a policy. For example, soon after the boxed warning in the United States in 2013, U.S. Army special forces, presumably on the basis of their long experience with bad things having happened from the drug, banned its use outright. I don't oppose those policies. I think those policies are quite wise. The drug simply isn't worth the risk in operational settings.