Tom Haudricourt initially reported that Braun's appeal was based on disputing the testing procedures, not his positive test. It looks like we've got more detail, and, oh man:
According to one of the sources, the collector, after getting Braun's sample, was supposed to take the sample to FedEx/Kinkos for shipping but thought it was closed because it was late on a Saturday. As has occurred in some other instances, the collector took the sample home and kept it refrigerated. Policy states that the sample is supposed to get to FedEx as soon as possible.
MLB is pissed, but these are the testing rules they agreed to, and they didn't follow the rules. If the procedure is so fucked up that some dude can keep a jar of Ryan Braun's pee in his fridge over the weekend, then maybe Major League Baseball should worry less about Ryan Braun's appeal and more about a chain of custody that relies on a courier knowing the hours of his local Kinkos.