President Joe Biden on Wednesday said he’s not sure whether the Supreme Court would block his plan to “forgive” hundreds of billions of dollars in federal student loan debt.

“I’m confident we’re on the right side of the law. I’m not confident about the outcome of the decision yet,” the president told reporters when asked whether he was confident that the nation’s highest court would rule in his administration’s favor.

The Supreme Court heard oral arguments on Tuesday in two cases challenging Biden’s use of executive power. At the core of the cases is the question of whether Biden has the authority to implement the $400 billion plan, which would cancel up to $10,000 in student loan debt for every borrower who earns less than $125,000 a year while canceling up to $20,000 for each Pell Grant recipient who meets that income standard.