Yes, indeed he can. If he neglects to keep accurate records he can be arrested.
Then, he is not using it properly and legally.
You moved the goalposts, dude!
And I showed that he could use the drug properly and still be arrested. It’s use has nothing to do with post-use record keeping.
“A product, when used legally- is always legal.”
If he uses the drug legally, then he cant be arrested. If he neglects to keep proper records, he is not using it legally.
Maybe a cocaine using physician could chime in. The record keeping is an administrative function that he could assign to an employee.
ETA: how ironic . . . You’re blowing smoke. 
Late to the party, but hey.
I certainly don’t hate smokers, but when I find out someone smokes, there’s a certain feeling of disappointment, a realization that they’re one of those people.
This is probably classism on my part to a degree. Practically none of my friends smoke, and no one at work smokes, but when I worked at a call center a few years ago, where most everyone was living hand to mouth, break time was almost universally smoke time. After a while, there’s an aspect of conditioning to it. Someone says they’re going out for a smoke and my heart just kind of sinks. Patronizing as hell, I suppose. I never pretended to be a good person.
To answer the OP’s question, I don’t hate smokers as much as I hate inconsiderate people, no matter what the vice.