I think this article is incorrect. I think they were alcohol related charges not drugs.
From a twitter account:
Aldon Smith has had tons of legal problems including multiple DUI and drug-related, assault weapons, vandalism, and domestic violence-related charges. But the Seattle Seahawks were desperate for a pass rusher
He was bad news for years. And from zerohedge where I picked up the article:
The following year, he was suspended by the league for nine games after violating NFL personal conduct and substance policies.
In 2015 there was more trouble as Smith saw the end of his 49ers days when they released him for being arrested on hit-and-run, DUI and vandalism charges.
After joining the Oakland Raiders, Smith lasted just a month before picking up a year ban for again falling foul of substance abuse rules.
Smith was dropped by the Raiders in 2018 for being picked up on domestic violence, assault and false imprisonment charges.