Sorry Reconn3, but the information you've been given thus far are incorrect.
Is this the gun in question?
If it is, please be advised that in Canada, there is no federal statute against selling very low powered, transparent airguns to minors. Most retailers have a policy against selling to minors, and many manufacturers label their products as 18+. However, that is not a matter of criminal law in Canada.
The only minor exception to the above is Ontario, where a provincial bylaw prohibits the sale of imitation firearms by businesses to minors. A very low powered, transparent airgun would indeed be an imitation firearm, subject to such bylaw sanctions. However, since that is an Ontario bylaw and you're in BC, that does not apply to you.
Again, I apologize for any confusion resulting from this thread. And I seriously advise members here to be damned sure their Canadian law, both federal and provincial, is up to scratch before commenting.