Now, the outgoing vice president is willing to give Sessions -- a former Senate colleague and President-elect Donald Trump's choice to become attorney general
-- a second chance.
"I wouldn't have appointed Jeff, but people learn," Biden said during an interview with CNN's Jake Tapper. "People change."
Acting as the highest-ranking Democrat on the Senate Judiciary Committee, Biden was instrumental in scuttling Sessions' nomination for the federal bench three decades ago. He told Tapper he "led the fight against him."
After the committee heard testimony alleging Sessions made racist remarks and called the NAACP "un-American," Biden publicly urged then-President Ronald Reagan to withdraw the nomination.
He went on to vote against him, making him only the second nominee in half-a-century to be denied a federal judgeship.
Sessions resolutely denied the charges of racism. He went on to serve with Biden in the US Senate for more than a decade. Biden said he'd spoken to the Alabama lawmaker on the Senate floor just this week during a visit to the Capitol.
"My general rule is that the president gets to choose who he wants or who she wants for their Cabinet members," Biden said, adding the one exception was if a nominee is "taking over the job with the expressed purpose of not enforcing the law in that area."
Biden said he hoped Sessions would uphold the law if he's confirmed to run the Justice department.
"Let's see what he says in his confirmation hearing. Let's see what commitment he makes," Biden said.
He expressed less confidence at Trump's choice to head the Environmental Protection Agency,
Oklahoma Attorney General Scott Pruitt.
Pruitt has rejected the conclusions of a vast majority of scientists who say climate change is driven by human activity. Environmental groups fear he will roll back regulations in a bid to bolster the fossil fuel industry.
"If he is going not to enforce the Clean Air and the Clean Water Act in the name of jobs, then that's not a guy you vote for," Biden said.