What?! If you don't let him start vaping, he'll start smoking? Please tell me that kind of adolescent extortion doesn't work on you.

Do what you would do with any unacceptable behavior - make if off limits and let him know there will be consequences if he's caught. 

Your son is breaking the law. Your profile says you're in CA. The legal age to buy tobacco for smoking, dipping, chewing, and VAPING is 21yo. If the shop is selling to underage people, report them.

I would also do some research on Vaping, because it's not true that it's not bad for them.

Why on earth does he feel he has to do one or the other?!

A 16yo is in your grill about anything and you are worried about vaping?  I would have immediatley plucked his tail feathers, grounded him for life, informed him that he will do only what he is told to do when he is told to do it or his life will become one of abject misery.

Now for the vaping... show him the medical information on PopCorn lung which is associated with vaping and inform him that having a child far worse than not having one and that you brought him into this world and you can take him out then march him to his room by a twisted ear, collect all of his electronics (phone, tablet, lap top, game system, etc....) dump them in the bathtub and drown them.

Then let him know that  you can keep this up for two more years until he turns 18 and can make his life a living hell so he better gain clarity and pull his head out of his ass or suffer.

https://www.medicalnewstoday.com/articles/318260.php

His logic is typical teen boy brain fart.  Counter his logic with "Slitting your wrists is less deadly than shooting yourself in the head yet they will both kill you.  Your logic is flawed and you are being an idiot.  Pull your head out of your ass and think instead of being a voluntary dipshit."

Bring the pain.  Don't allow him to dictate anything.

"ok so you decide to vape or smoke against the law and it's against my house rules. say goodbye to your cell phone, video games, and friends nights out. also to driving since I can't have a distracted driver who might wreck my car. Down the road you can say goodbye to a high sperm count, and hello to erectile dysfunction. then finally a slow agonizing death from lung cancer or just about any other type of cancer." 

Be his parent and ground his a**.

I vape because nothing else has helped me break my addiction to cigarettes. But why the hell would you want to become an addict in the first place?

Im quite sure it's better than smoking, but inhaling any additional chemicals into your lungs you dont need to surely is not 'safe'. Its cheaper than smoking, too - but it's still money I could be using on other things. 

Unfortunately you cant stop your kids from doing stupid things, but you don't have to keep quiet about it and you don't have to tolerate in your house or in your presence. 

Vaping is not the problem. The problem is you clearly have not maitained the proper parent/child relationship if he is "telling you how it's going to be".

You need to enforce a proper parent/child relationship or this will likely be the least of your worries. 

I would rather my son smoke cigarettes than vape. There are greater dangers to vaping than smoking! All the BS around vaping being a safer option is nonsense! He should be shown a medical journal or research site rather than an advertisment for slow suicide over time!

In both instances, my son would get into huge trouble with me because both are hazardous to your health in the long run.In the UK you can not buy smoking related stuff (vapers or cigarettes at 15). Where is he getting this stuff? I would report who ever is selling this stuff. Also I would march my son down to the police station and have them give him a good talking to about breaking the law!

Step UP and be a parent.

NOT IN MY HOUSE YOU DONT and not on MY property. When you are 18 and move out you can vape all the way to the moon and back if you want.

Like everyone else stated. BE THE PARENT. End of story. 

Grounded, take the keys, lose the TV, room searches, etc. -- be the parent. You can do this. 

Your kid sounds like a little snot who has never heard "no."

You probably loved being the good guy, the cool parent, and your kid's friend all these years. Well, that ride is over!

This is why kids need to hear "no" when they're young. You have no authority over this kid and he's not even 16 yet! And NOW you think you're going to impose "no" when he's doing something dangerous? Good luck with that.

Why did you wait so long to be a parent?

This is a UK article..

https://publichealthmatters.blog.gov.uk/2018/02/20/clearing-up-some-myth... 

...and so a lot of the stuff in it is not necessarily relevant to a US consumer. However, much of it is probably true in the US as in the UK (except the regulatory stuff - I have no idea). It is much safer to vape than to smoke. (However, it is infinitely safer to do neither.)

BUT your teen is coming up with a BS argument of either/or. That's crap. And I suspect he knows it, too. It's not even clear that vaping leads to smoking (but it sure leads to a nicotine addiction which can lead to smoking). You could, if you wanted to, take a harm reduction path on this and encourage him to choose only very low mg nicotine products - at least that would make it easier to quit when he comes to his senses. 

Your teen isn't even a good troublemaker. What kind of teen makes that kind of ultimatum without having been busted first. He's basically just tattled on himself. I don't know whether to be proud or worried, but I cannot imagine my son (just 11) saying something like that to me. He'd basically just do it and keep it on the sly or try to - I think I'd rather be in your shoes. 

put other drugs into unite and vape them. In liquid form, and flavoring added. You can not tell what they are vapeoring

This young man has just challenged you to a duel, and is using Vaping as the gauntlet to throw down.

Don't be as appalled by the vaping (which IS bad ENOUGH on its own!), but by the fact that he CHOSE to essentially slap you while your husband was out of town.

Treat it as if HE SLAPPED YOU.

What are you going to do about that?

That's the problem, he's rebelling. I'd imagine, "Wait till your father comes home" might be an option.

Maybe, "Nnnnope. You might vape when I'm not looking, I can't control that. But as long as you live under this roof, no one harms themselves or anyone else. And vaping is EXACTLY that. So, NO. You will now produce all of your vaping supplies and paraphernalia - or you may wait till your father gets home and produce them for him, though I'm quite sure it'll come with some extra strings attached."

I believe I heard that vaping oils come with up to 20x the nicotine that tobacco in cigarettes has. If it matters at all (and it doesn't much, because it's a fact, proven in the halls of medical academia), nicotine constricts blood vessels and causes a lot of strain on brain tissue, the heart, and other vital organd, including the kidneys, which can cause chronic health issues, including renal failure. But of course, his article probably forgot to mention that while focusing on particulates in smoke.

He's a misguided kid who doesn't know what he's doing. And now he practically slapped you. Don't accept that.

I'm sitting at my desk trying to imagine my son telling me "hey mom I'm a vaper" to which I'd reply the h@ll you're not. How this kid comes up to you and tells you what he "is"?!? I'd give him a dose of reality and if this is something that he thinks is cool to do than he needs to get in a sport and do something that keeps him busy because he has too much time on his hands.

LOL mom I'm a vaper!!!! Yeah whatever!

Half these kids don't even know how to wipe their own @ss but they're going to tell you what they are hahahaha.....this is hilarious to me!