It is certainly nicer when your partner is truthful, but I cannot comprehend the worldview that holds that his being untruthful is so horrible while her turning his house into a security checkpoint a la those at international airports is OK. Nor how OP's trying to change his behavior that is harmless to her is OK. How did she suffer from his smoking pot? Why was it her business? Was it a legal concern? Well, then she should have banned him from smoking in her house (where she could have suffered legal consequences), but in his own house he should be free to do whatever he wants.

Is OP is against the drug, there are other ways to act on this strong opposition. She can join organizations that make it their goal to oppose marijuana; she can donate money towards the marijuana raids efforts, etc. It is not necessary to take this opposition on one's near and dear. Why single out the boyfriend? Reach out to masses of people instead; make a scalable impact, for goodness' sake. Limiting one fellow's consumption is a drop in the bucket anyway, so why expend energy on it.

Is he even an addict? No, per OP verbatim, he "enjoys smoking weed". That is all - "enjoys". And per the title of the thread, he does it "too much". So who decides the norms of weed consumption and on what (hopefully non-arbitrary) basis are those decisions made?