During the presidency of Barack Obama, the government eased enforcement of federal marijuana laws in U.S. states permitting cannabis use. This made massive strides compared to the Bush administration because Bush didn't do anything at all to ease federal marijuana laws. This also applies to the every other administration before him including Nixon administration.
Contrastingly, 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."
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."
See also
Cole Memorandum
Eric Holder, served as the 82nd Attorney General of the United States from 2009 to 2015 Michele Leonhart, former Administrator of the Drug Enforcement Administration Political positions of Barack Obama