Von Miller is potentially subject to a suspension of four games for what Adam Schefter called a violation of league rules. [UPDATE: Miller says he knows he did nothing wrong] That is a pretty broad category. According to Mike Klis of the Denver Post, Miller had previously tested positive for amphetamines and marijuana back in 2011, his rookie year in the league. Brandon Kristal of 104.3 The Fan is reporting that the positive test is for weed and “molly”, a form of MDMA (methylenedioxymethamphetamine).
It should be noted that by the terms of the Policy and Program for the Substances of Abuse, a first failed test, like that now being reported from 2011, would have put Miller in a program, without suspension, so long as he complied. That information and involvement in the program is supposed to be confidential, and anyone that violates that is subject to a fine of $10,000 up to $500,000.
Unless a player fails another test while still not completing what is called Stage One (90 to 270 days after entering program), it could actually take two more failed tests while in what is referred to as Stage Two of the program to trigger a four game suspension. A first failed test while in Stage Two could result in a fine of four game checks, but not a suspension. Cocaine, marijuana, amphetamines, opiates and opioids, PCP, and MDMA are drugs covered under the drug policy. It should be noted that this program is separate from any violations for performance enhancing drugs.
So if you were wondering how he could have a positive test in 2011 and just now be getting suspended, it is more likely that he has had three failed drug tests.