The issue with this is it is his second offense and quite possibly this positive test was before being traded to DET, even though it is just coming out. If this is the case, how is this not about DD doing his due diligence. And even if the test is after, there is still a concern of acquiring a player with a past performance issue.
"Just weed" is a cop out. No one says "just alcohol" when a player gets in trouble with that. Weed is as dangerous as alcohol, if not more. There are few examples in pro sports where highly talented athletes end up out of their games at early ages due to weed use.