Congress never directly authorized the president to forgive student loans. Biden was claiming that he had the power indirectly because of a law that says he can

Congress never directly authorized the president to forgive student loans. Biden was claiming that he had the power indirectly because of a law that says he can "modify" loans in times of "emergency" (this was used to pause repayment in 2020). But SCOTUS has ruled that fully forgiving them too far beyond merely "modifying". There is a principle called the "major questions doctrine" that any major action must be very explicitly authorized by Congress (i.e. Congress doesn't grant huge powers without saying so).