"Since the campaign, President Trump has consistently supported states' rights to decide for themselves how best to approach marijuana," Gardner said in a statement.
"Late Wednesday, I received a commitment from the President that the Department of Justice's rescission of the Cole memo will not impact Colorado's legal marijuana industry."
"Because of these commitments, I have informed the Administration that I will be lifting my remaining holds on Department of Justice nominees," Gardner added.
The Washington Post first reported the development, and the White House confirmed on Friday Gardner's statement was accurate.
In January, Attorney General Jeff Sessions revoked the Cole Memo, Obama-era guidance designed to discourage prosecutors from targeting states that have legalized marijuana. The move provoked an outcry from marijuana friendly states, including Gardner's Colorado, in which the marijuana industry has flourished since 2000.
Angry that Sessions had reneged on his pledge to leave marijuana states alone, Gardner promised to block all DOJ nominations, pending a resolution.
Since then, he has held up about 20 Justice nominations, the Washington Post reported.
"Clearly, we've expressed our frustration with the delay with a lot of our nominees and feel that too often, senators hijack a nominee for a policy solution," White House legislative affairs director Marc Short told the Washington Post on Friday. "So we're reluctant to reward that sort of behavior. But at the same time, we're anxious to get our team at the Department of Justice."
Trump "does respect Colorado's right to decide for themselves how to best approach this issue," Short added.
Gardner and other senators have been discussing legislation that would prevent federal government intervention in states that have legalized marijuana. Nothing has been finalized, according to Gardner's statement.
"My colleagues and I are continuing to work diligently on a bipartisan legislative solution that can pass Congress and head to the President's desk to deliver on his campaign position," Gardner said in a statement.
This move comes days after former Republican House Speaker John Boehner announced he would join the board of a medical marijuana holding company. Advocates have called this announcement a watershed moment for the marijuana industry.