Well, speaking from the parental point of view, if he's a minor child whom his parents support, if they don't want him smoking, he continues to smoke in the coming weeks, and if they do take him to a lab to have the drug test in a month, he will definitely test positive.

If he's made up his mind to do what he prefers/smoke anyway and has made his peace with the withdrawal of whatever privileges his parents take away once that positive test comes back, I wouldn't say he has to worry.

But if I'd felt strongly enough to test my son for drugs after making the you-must-stop edict and he'd gone against us, he'd be risking the loss of car, other-than-essential financial support including cancelled car insurance, computer, cell phone and related DSL/cell subscriptions. Possibly also several favorite shoes and outfits. I mean he'd lose all of them, not just one or two. Maybe his parents aren't serious about the edicts they lay down, but if they are, this'll likely be a serious infraction.