There are free agents, and there are free agents. The clubs get the notice of a positive test before the suspensions are announced. So what do clubs do to some of these guys who tested positive? The clubs release them, then the positive test is announced. Voila - a free agent tested positive; no club is tarnished.
So far this year almost the same number of milb players tested positive as in EACH of the prior two years.
And yes, the U.S. players tested more often positive for pot (a drug of abuse for MILB, but not for MLB [who the heck knows why but that's the rule]) then PEDs from an earlier era. But Latin players make up about a third of pro players, and the DSL seems to have a real problem.
But I can't see how that justifies MLBs head in the sand policy. I was always amused by the thought that a player can show up dead drunk for his test and be fine, but a player who took a hit of pot two weeks before can be suspended.