Von Miller is currently in stage 3 of the leagues substance abuse policy. You do not get to stage three for 1 violation. His next failed test is 1 year off (same ironically as Gregory).
(Please note I am not making any comparison between the two players just where they are in the substance abuse program)
http://www.nfl.com/news/story/0ap10...-suspended-six-games-for-nfl-policy-violation
"Rapoport later added that Miller now is in Stage 3 of the league's program and policy for substances of abuse and his next violation
carries a minimum one-year suspension, according to a person informed of the player's situation. Per the policy, Miller will stay in Stage 3 for the rest of his career."...
"NFL.com's Albert Breer reported Monday, according to two sources, that a diluted sample
caused Miller's most recent violation of the NFL's substance-abuse policy."