The first thing regarding investment is that the convention itself doesn't require states parties to criminalize investment and a number of states parties probably would have had concerns if that had been suggested in the negotiation.
“Investment” is not a term that is all that well known to criminal law, and using it in a defence would have posed a great deal of drafting difficulties and potential over-breadth. In Canada there are also federal-provincial divisions of powers issues that would have had to be dealt with.
What has been done instead is to incorporate the law of aiding, abetting, and counselling in clause 6 of the bill. What that means in practical terms is if someone in Canada invests in a company either in Canada—a company in Canada would be prohibited from doing this anyway, but if someone invests in a company outside of Canada that is engaging in prohibited conduct, a question of remoteness would arise. If someone's pension plan has a few shares in a company that does a lot of things, that possibly makes cluster munitions, then criminal liability doesn't attach. If it is close enough that it constitutes aiding and abetting, that it meets the case law for aiding and abetting, then it would.