If you took out student loans before July 1, 2013, you may be paying an interest rate as high as 7 percent. But if you took them out on or after that date, the highest rate you’ll have to pay is 3.86 percent, thanks to legislation enacted in 2013.

Sen. Elizabeth Warren (D-Mass.) wants to allow student borrowers to refinance at the new, lower rate if their loans are still set to the old, higher rate. On Wednesday, she introduced a proposal in Congress, the Bank on Students Emergency Loan Refinancing Act, that would do just that.

Under the bill, all federal and private student loan debt acquired before July 2013 would be eligible for refinancing with the government at a lower, fixed interest rate. That means millions of former students would see their monthly payment amounts reduced for the entire length of their loan repayment. Borrowers of private loans would have to show that they are currently in good standing with their lenders to be eligible.

According to Young Invincibles, the bill would provide relief to more than 25 million student loan borrowers.

“Young people who are working hard to build a future deserve a real opportunity to succeed and that means letting struggling borrowers refinance their student loans to take advantage of lower interest rates – the same way people refinance a mortgage, a car loan, or business debt,” Warren said in a statement announcing the bill. “The Bank on Students Emergency Loan Refinancing Act would give much-needed relief to millions of borrowers, help boost our economy, and strengthen America’s middle class.”

So who would oppose such legislation? Well, big banks and private student loan companies. Private lenders would see a loss in revenue resulting from smaller interest payments that would be higher under their current rates. (The government would pay off the privately held debt for people who refinance.) Private lenders originated about 10 percent of currently outstanding student loans. Those companies include Sallie Mae, Wells Fargo, and Bank of America, among others.

And while the bill wouldn’t cost the government much money to enact, it would similarly result in less revenue down the road as lower interest rates mean smaller interest payments from student loan borrowers. If that revenue is not replaced with another source, the deficit would increase. That would likely be an issue for fiscal conservatives.

The bill is not likely to pass in the current session of Congress. The Senate rejected a similar bill last year, and the vast majority of Republicans voted against it. Now, Republicans control the Senate.