The Federal Communications Commission (FCC) today, as long expected, formally approved T-Mobile US’ merger with Sprint along party lines. While the move is a positive development for both companies, which have been fighting for the deal for almost 18 months, it could still be upended by a lawsuit filed by a group of state attorneys general that want to block the transaction.

T-Mobile US garnered hard-fought approval from the Department of Justice (DOJ) to acquire smaller rival Sprint in July, but the deal has been beset by legal challenges and opposition from multiple organizations ever since.

Lawyers and policy directors representing the Communications Workers of America (CWA), Public Knowledge, and the Rural Wireless Association held a press call today to lambaste the approvals by the FCC and DOJ, particularly the settlement agreement the latter worked out to set the table for Dish Network to acquire some of Sprint’s assets and become a viable 5G operator.

“The DOJ settlement sets up a Potemkin village, one that is all facade with no solid structure or foundation,” said Debbie Goldman, telecommunications policy director at CWA, in a prepared statement. “It fails in multiple ways. The DOJ settlement leaves Dish dependent on T-Mobile’s network for seven years, making Dish T-Mobile’s largest customer, not a competitor.”

Phillip Berenbroick, policy director at Public Knowledge, argued that the merger would harm consumers and leave the market vulnerable to anticompetitive behavior including higher prices and reduced innovation. “The DOJ’s proposed remedy is unlikely to reliably protect consumers,” he said in a prepared statement. “The DOJ has clearly given little or no consideration to the complexity, cost, and execution risk that could derail Dish’s hoped for entry into the wireless market as a fourth facilities-based provider.”

T-Mobile US and Sprint maintain that only a combined entity will create the spectrum assets, scale, and financial wherewithal necessary to make it and the nation a leader in 5G. “The combined company will deliver superior coverage, capacity, and consistency of experience at better prices than either company would be able to offer as a standalone,” a Sprint spokesperson said earlier this month.

Sprint is also is in the awkward position of denigrating itself and warning of imminent doom if the merger isn’t consummated. Sprint wasn’t the first domestic operator to deploy 5G, but with nine markets now activated and a coverage area considerably larger than AT&T, T-Mobile US, and Verizon, it is providing the most robust 5G service today, according to analysts.

FCC Commissioners Jessica Rosenworcel and Geoffrey Starks, the two Democrats on the commission, voted against the deal and issued statements explaining their decision. The other three commissioners, all Republicans, voted in favor of the merger and declined to provide statements after the vote.

“We’ve all seen what happens when markets become more concentrated after a merger like this one,” Rosenworcel said in a prepared statement. “There’s no reason to think this time will be different.” She also called out the majority Republican commissioners for agreeing to approve the transactions months before legal, engineering, or economic analysis was completed.

Starks described the settlement with the DOJ as a “paper-thin commitment” that fails to mask reality. “You don’t need to be an expert to know that going from four wireless carriers to three will hurt competition,” he said in a prepared statement. “This merger takes a bad situation and makes it worse.”

He also criticized Sprint amid an ongoing investigation into “what appears to be the largest unlawful collection of universal service funds in FCC history.” He added: “The obligations imposed on the parties are so loosely drafted that meaningful enforcement will be impossible. The financial penalties for non-compliance will not effectively deter a company with billions of dollars in annual revenue.”

DOJ officials are reportedly in discussions with the state attorneys general to alleviate their respective concerns, but there has not been any breakthroughs yet, and the lawsuit isn’t schedule to reach a trial start date until Dec. 9.