I think the bigger issue is the discrepancy between samples. One under and the other just over. I don't think he should go with secondhand smoke. The league doesn't care if a player ingested a tainted supplement, why would they ease up on a guy who unintentionally inhaled weed?
Given appropriate lab technique the two samples should be identical. The units of measurement are so small, and the samples are so small that a fraction of a drop could throw the numbers off. I'm actually shocked a 1/2 result would be positive because the B sample is usually considered confirmatory test of A and if the result don't match how can you say it's positive?
I'm also shocked that the NFL doesn't go by the federal cutoff (which I believe is 50 ng/mL) when enforcing a federal law.
Also, I'm not entirely sure but I think if the first sample comes back negative they don't even test the second sample. A negative on the A sample is generally considered good enough to conclude that the sample is negative. Positive results require a confirmation test. Had his B sample been tested first they probably wouldn't even test the second sample and he never would have came back positive.
I don't see how the suspension can be upheld given a 1/2. It would not shock me if he won the appeal, but I doubt the league is all that concerned.
If you want a conspiracy, the NFL has contrived the test results as a means to excuse his test just so they can take some of the heat off for the Ray Rice ruling.