The interstate commerce clause has been used as a dumping ground for federal overreach for a long time. It is likely that it was only intended to provide authority sufficient for the federal government to prevent a state like Missouri from treating Colorado cannabis any differently from California cannabis, if either happen to be imported into its jurisdiction. This interpretation is considered obsolete by many federal judges.
Interpreting it such that a cannabis plant grown, harvested, prepared, and consumed entirely within the state of Colorado, exclusively by Colorado persons, may still be subject to federal law is a bit of a stretch, in my opinion. But the prestigious paid professionals still do it.
It took the 18th Amendment to prohibit "the manufacture, sale, or transportation of intoxicating liquors...for beverage purposes" at a federal level in 1920. The Volstead Act was able to use that amendment as the basis for its authority. The 21st explicitly repealed it, thus obviating Volstead, which had already been unpopular for years. Note also that consumption was never outlawed. Even so, it was a disaster.
There was no such amendment to authorize prohibition or control of other, non-alcoholic intoxicants for recreational purposes. What happened to the Constitution between 1920 and 1970 that would have allowed Congress to pass another prohibition law like the Volstead Act? Nothing. Nothing at all. Or rather, New Deal politics happened. Federal power expanded without explicit authorization, just because of a temporary confluence between economics and political opportunity.
The various drug war laws are probably not authorized by the commerce clause, just as justices O'Connor and Thomas dissented (Rehnquist concurring with O'Connor) in Gonzales v. Raich [0]. It would seem that, looking also at Wickard v. Filburn [1] and US v. Lopez [2], the SCotUS is not likely to be of any help here. The underlying argument is that "drugs can be sold, therefore there exists an interstate market for them, therefore federal regulations on them are authorized by the commerce clause." Wickard v. Filburn seemed like politically-motivated bullshit to me, but who am I to argue with the precedent?
The laws will, like Volstead, mainly be overturned by the court of popular opinion long before any official federal action occurs.
[0] https://en.wikipedia.org/wiki/Gonzales_v._Raich
[1] https://en.wikipedia.org/wiki/Wickard_v._Filburn
[2] https://en.wikipedia.org/wiki/United_States_v._Lopez