Nick Diaz uses marijuana.  He tells everyone that will listen to him that he uses marijuana.  He has a mild disability that marijuana helps him with.  Never mind that pills are probably better for him, and who knows which is best for getting hit in the head. California and Nevada have very liberal medical marijuana use laws. The UFC formerly used the expensive test that was ungodly accurate. Under the former test Diaz could have easily passed the test pre-fight, then flunked the test post-fight. Heavy marijuana users tend to store marijuana metabolites in their fat cells, and sweat them back out under stressful situations.  He claimed that he stopped using marijuana eight days before his fight.  His score was so low that detection should have made someone´s momma proud.  That is what got Diaz a one year suspension. After the UFC got wind of the facts, [from yours truly] they started using the cheaper, less accurate test.  For some reason Diaz was tested three times for a later fight. This created conflicting evidence. Big surprise.

Marijuana metabolites have a half-life. The amount of metabolites in the blood diminishes on an exponential scale. That means that it goes away really fast. Again, Diaz had low scores.  Diaz was his usual disrespectful self.  As is also usual, men in a position to make discretionary decisions look for a way to abuse that power.  So after collecting conflicting evidence, the Nevada Athletic Commission suspends Nick Diaz for five years.  Both times he opted to hire in-your-face lawyers to advocate for him.  Both lawyers caused long delays when they should have asked for justice tempered with mercy.  Hotly contested cases have to be prepared for, and later appealed.  His license to fight has been suspended since his last fight, Jan 31 2015.