The answer is No.
Unlike Heroin, Morphine, Oxycodone, Speed, Amphetemines, Xanax, Valium, Opium, Caffeine, Nicotine, and Alcohol...
Cannabis (pot, weed) does not contain any addicitve substances.
The experience of smoking pot; however, is quite pleasureable. It is a euphorant and ellivates the mood very rapidly entering the bloodstream when imbibed in the the usual manner through the lungs as inhalation of THC and other cannabinoid vapors from smoking (nb: vaporizing is one smokeless method, consumption in food or drink is another.)
THC, the most active ingredient in cannabis also has an analgesic effect and an anti-inflamatory effect. If your husband has any injuries that hurt him, he's not only feeling "high" he is feeling less pain.
Cannabis use increases the sensations, and therefore the effects of other intoxicants. If your husband likes a beer with his smoke, he is getting a bigger bang for his alchohol use. Is drinking beer and other beverages of that sort a normal part of your day? There is a link between alchol use and diabetes. If he is drinking, perhaps he is dealing with the emotional aspect of a blood sugar problem?
You already know that asking, demanding, pleading and threatening your hsuabnd to stop smoking pot doesn't work.
So what should you do to get him to stop? Talk with him. Find out why he is smoking. Find out how you can help him feel better, happier, more comfortable. He won't stop doing what is making him feel better until he feels better and no longer has to do what he is doing.
It sounds like he is self medicating any of a number of things I outlined above -- stress and depression (and using pot as a euphorant); aches and pains (and using it as an analgesic and antiinflamatory); increasing the effects of the alcohol buzz or the blood sugar rush (maybe he needs a check up -- our Dear Husbands tend to think they are invincible sometimes and do need our help to take care of themselves.) And it could be a combination.
This is where being a partner, going the extra mile, sucking it up and being the Woman who Stands By Her man comes into play. This is being Married.
It will take time and compromise on both your parts. And don't forget to celebrate the victories -- even the small ones. He may cut back a bit he may cut back a lot. You will both certainly be handling the situation as loving and caring pair of adults in a partnership.