The U.S. Postal Service has filed yet another petition against the mandate that it end emergency price hikes, once again dragging out a process that has already lasted years.

USPS made its filing with the U.S. Court of Appeals in Washington, D.C., on Friday, just weeks after its regulatory body issued a ruling in compliance with a remand from the same court in June. The Postal Service had challenged an initial decree from the Postal Regulatory Commission that the exigent price increase could not continue indefinitely, but the courtsided with the PRC.

The appeals court also instructed the PRC to allow the Postal Service to collect some additional revenue from the higher rates before they expire. USPS is now challenging PRC’s subsequent ruling that allowed the agency to earn an extra $1.2 billion from the temporary price increase.

With the appeals court already having weighed in on the subject, it is not clear exactly what the Postal Service hopes to gain from once again bringing the case before it. A USPS spokesman declined to comment on the petition, but some of the agency’s biggest customers have some ideas of their own.

Stephen Kearney, executive director of the Alliance of Nonprofit Mailers, called USPS’ petition unfortunate “but not surprising.”

“Many expected this move, not because the USPS is likely to have strong legal grounds to overturn a very well done PRC decision, but more for political reasons to support action in Congress that would overrule both the regulator and the U.S. Court of Appeals by making the surcharge permanent,” Kearney wrote in a message to members.

Sen. Tom Carper, D-Del., is once again working on a postal reform package, as he has in each of the last two congresses. Those efforts received bipartisan support but ultimately fizzled out. He is expected to unveil his latest proposal later this year.

Kearney said the Postal Service’s latest stalling tactic could draw out the legal process for months, continuing the ongoing uncertainty for large-scale mailers.

“It is very difficult for customers to realize that with this USPS they do not come first, but rather last,” he wrote. “Once again, litigation and legislation come before the organizations and companies that pay the freight and stay with the Postal Service through thick and thin.”

The Postal Service asked for and instituted the exigent rate hike in 2013, citing the effects of the recent economic recession on its business to justify the 4.3 percent increase. Under a 2006 law, USPS can only raise its prices by the rate of inflation except under extraordinary circumstances.

With significant controversy, the Postal Service argued in 2013 the recession constituted such a circumstance, and the PRC obliged, but set a cap on the amount of money USPS could bring in as a result of the higher prices. The mailing agency was originally set to hit that ceiling this summer, but the subsequent court and PRC rulings extended the timetable into the spring of 2016.