10th Circuit says that it's constitutional to prohibit felons from possessing firearms

[ET Awful]

4. And the 5th Circuit ruled that it's unconstitutional to bar gun ownership based on drug use.

Just last month they made that ruling. It's not necessarily immediately applicable to Hunter Biden, but it is usable as a defense (and I have zero doubts that his attorneys will use it).

https://www.reuters.com/legal/drug-user-cannot-be-barred-owning-guns-us-court-rules-2023-08-10/#:~:text=Aug%209%20(Reuters)%20%2D%20A,year%20that%20expanded%20gun%20rights.

Basically boils down to treating drugs the same as alchol - you're prohibited from carrying a gun while intoxicated, but it does not bar ownership or bar someone from carrying when sober because they were intoxicated or high at some prior time (or subsequent time).