You're missing the point. How many athletes get charged with simple possession?
If it is in line with the general population aged 18-23, it is a lot higher than you would think. And this is being conservative.
It is no different than speeding tickets, disorderly conduct, DUI etc.
Just look at your average draft. You hear about the high profile college players who have gotten into trouble. But how about the unheralded player who did not get much national attention?
If they were to suddenly enforce rigid criminal background records on NFL-ready players, that would cut into the talent pool immensely.
If they did, half the NFL would have records and probably more than three quarters the NBA.
How do you know what their records are? For all we know a decent percentage of athletes entering the professional realm have some sort of an arrest record. It might be some misdemeanor, but it is there.
If this league says "no criminal record", like say an employer that knocks out drug offenses, crimes involving violence and theft, good luck getting talent.
Even a lot of the kids from less than ideal backgrounds make it through the collegiate system. They mainly face trouble when they get drafted and make it to a roster. It's the NFL enforcing the law not the federal gov't. NFL suspension does not equal criminal record.
More kids get into trouble and it is not publicized. You only hear about the half of it. There is a reason why sometimes nobody can explain why some draft prospect tumbles. Sometimes it is because they had some minor issues that turned up as teams started digging into their backgrounds.