The bill states it is intended "to prevent unjust and irrational criminal punishments," Roll Call reported Wednesday.
"Our reliance on mandatory minimums has been a great mistake," said Sen. Patrick J. Leahy, D-Vt., chairman of the Senate Judiciary Committee and co-sponsor of the bill with Rand Paul, R-Ky.
"It is time for us to let judges go back to acting as judges and making decisions based on the individual facts before them," Leahy added.
Mandatory minimum laws "reflect a Washington-knows-best, one-size-fits-all approach" that undermines the separation of powers, Paul said.
Under current law, federal judges can only depart from mandatory minimum sentences for drug-related crimes. The proposed legislation wouldn't require judges to be more lenient. If they did so, the judges would have to state on the record why they ordering less than the mandatory minimum sentence.
The bill was introduced as federal prisons are 38 percent over capacity. The Senate's fiscal 2013 continuing resolution directs the Bureau of Prisons "to undertake a comprehensive analysis of its policies and determine the reforms and best practices that will help reduce costs and recidivism."