During the presidency of Barack Obama, the government eased enforcement of federal marijuana laws in U.S. states permitting cannabis use.[1][2][3] This also applies to the every other administration before him including Nixon administration.[4]
In contrast, Time reported in 2012, "Two years [after his first year in office], the Obama Administration is cracking down on medical marijuana dispensaries and growers just as harshly as the Administration of George W. Bush did."[5]
According to Jessica Bulman-Pozen and Gillian E. Metzger in 2016, "in declining to enforce the federal Controlled Substances Act with respect to marijuana offenses in Colorado and Washington, the [Obama] Administration has accommodated those states’ decisions to legalize recreational marijuana use."[6]