The landscape around pro sports leagues and marijuana are changing in the United States. There are now 10 states that have legalized recreational use of marijuana even with marijuana still being illegal on a federal level. This is a strange dynamic, to say the least. Nothing better states this dynamic like the rules on marijuana use and professional sports.
Professional Sports Leagues Marijuana Policies
NFL:
The NFL’s Policy and Program on Substances of Abuse, “marijuana and synthetic cannabinoids” are on the list of illegal substances even “passive inhalation” being deemed an inexcusable defense. The NFL did raise their threshold for drug test failures in 2014 but the Leagues threshold is still 75 percent below the Olympic standard.

Typically the NFL only performs one drug test per season and is done during the pre-season training process. Random drug tests can be performed though if the team request it or if a player is in the NFL’s drug program. Even with states beginning to rapidly legalize cannabis the NFL’s commissioner Roger Goodell is not convinced that marijuana use is good for players.
Stating to ESPN in 2017 “Is it something that can be negative to the health of our players? Listen, you are ingesting smoke, that’s not usually a very positive thing, people would say. It does have an addictive nature. There are a lot of compounds in marijuana that may not be healthy for our players long-term. All those have to be considered,”
Of course, this same feeling isn’t shared by all the NFL’s players. There have been countless interviews where players have said that cannabis use can help them ease the pain from years of strain on their muscles. Mike James even went as far as to apply for a medical exemption with the league so he could use cannabis for medical purposes. His request was unfortunately denied.
MLB:

The MLB is no stranger to being in the spotlight for having players that have drug problems especially those that enhance performance. Even with this, the MLB is far more relaxed on their drug screening then the NFL. The MLB defines drugs of abuse both synthetic and natural cannabis, opiates, and ecstasy.
These drugs of abuse are tested and suspended for during the minors, the majors do not test players as part of the regular season unless there is deemed a reasonable cause for testing. Even then if a player fails a test they are fined instead of suspended. You can read up more on the MLB drug policy here.
NHL:
Now with cannabis being legalized in Canada, you may be asking if the NHL will be the first league to change professional sports and the stances on marijuana. When Commissioner Gary Bettman gave an emphatic no, declaring “The Substance Abuse & Behavioral Health Program for decades has been educating players on using drugs, legal or illegal. … We think based on the educational level and what we do test for and how we test, at least for the time being, we’re comfortable with where we are.”

Marijuana is not necessarily a banned substance in the eyes of the league. Players are randomly drug tested two times during the season, one-third of the players are then selected from that group for advanced testing. One of the drugs tested for cannabinoids. Positive tests are not publicized or penalized but referred to the NHL and NHLPA’s performance-enhancing substance council for review. If deemed necessary players may have to be apart of the league’s substance abuse program. No suspension is attached to this program.
While the use of marijuana is still mainly frowned upon by the NHL a former player and front office executive estimated that 60-70% of players use marijuana for recreational use or pain management.
NBA:

The NBA tends to be the most progressive league in pro sports. Their current stance is surprising with the league having even a lower threshold then the NFL. No exemptions are giving for medical use there is no penalty though till the third infraction. Their penalty is a five-game suspension and then 5 sequential games for every violation after that.
The NBA also has 4 random drug tests for every player during the regular season as well as 2 during the off-season. More tests can be requested if deemed necessary by the team.
Now commissioner Adam Silver is currently reviewing the league’s stance on illegal substances. He even stated in an interview with Howard Beck ” We should follow science, This is not a moral issue for me, It is not an ethical issue for me. I obviously see what’s happening in states around me.” So it might not be too long till we see the NBA at least relaxing their strict rules on marijuana.