If it were legal, I don't think you'd see people secluding themselves or hanging out with their "pot crew" only. I suspect that even though recreational use remains illegal in ND and most other states, using marijuana is not as socially isolating as you are making it out to be. Remember when we were 14, and the kids who drank or smoked cigarettes were on the fringes, judged by most of us to be making poor decisions? Those kids hung out with their "alcohol crew", devoting substantial resources to obtaining alcohol. As we got older, more and more people started drinking underage and it became something acceptable within more and more social circles. I think the same is happening with weed. Not because as teens get older it becomes more acceptable, but just because it has become more acceptable in general.
I think we need to be concerned about this player's arrest, particularly if my thought that marijuana use is not so socially isolating, because that may mean plenty of other players are using it and are at risk for being arrested as well. In the 2014 NCAA survey of athletes, 23.5% of football players reported using marijuana within the previous 12 months. They have data showing that D-III athletes were the most likely to have used overall, but that's not broken down by sport. http://www.ncaa.org/sites/default/files/Substance Use Final Report_FINAL.pdf
I found this article rather enlightening: http://bleacherreport.com/articles/2486218-banned-but-bountiful-marijuana-coveted-by-nfl-players-as-invaluable-painkiller
Here's an excerpt:
"It's at least 60 percent now," Anderson said. "That's bare minimum. That's because players today don't believe in the stigma that older people associate with smoking it. To the younger guys in the league now, smoking weed is a normal thing, like having a beer. Plus, they know that smoking it helps them with the concussions."
That's from an interview with Jamal Anderson, formerly of the Falcons, discussing marijuana use in the NFL.
*edited because I screwed up the number of months in the NCAA usage study.