“The court has some serious concerns regarding the companies’ efficiencies claims,” U.S. District Judge John Bates, who presided over the 13-day trial, wrote in his 158-page ruling. “It is very likely that a significant share of the claimed efficiencies may be retained by the merged firm rather than being passed on to consumers.

Bates called the merger “presumptively unlawful” in the market for private Medicare Advantage plans.

He said his conclusion “is strongly supported by direct evidence of head-to-head competition as well. The companies’ rebuttal arguments are not persuasive.”

The Justice Department had also alleged that—in 17 counties across Florida, Georgia and Missouri—the deal would reduce competition for health insurance sales through the Affordable Care Act exchanges.

While the deal was still being reviewed, Aetna told federal antitrust regulators that it would reduce its presence on the exchanges in 2017 if the Justice Department sued to block the Humana deal. Aetna later delivered on that threat.

In his decision Monday, Bates found that Aetna pulled out of the exchanges in those 17 counties “specifically to evade judicial scrutiny of the merger.”

Aetna’s lawyers, led by John Majoras, a Jones Day partner, at trial defended the health insurer’s withdrawal from Affordable Care Act markets.

Majoras said Aetna made the decision not in response to the government’s lawsuit but as a business decision to avoid “hundreds of millions in losses” that the insurer expected from continued participation in the exchanges.

Majoras wasn’t immediately reached for comment Monday.

Hours after Trump took the oath of office Jan. 20, he signed an executive order that said the administration will move to repeal the Affordable Care Act.

His executive order directed federal agencies “to ensure that the law is being efficiently implemented, take all actions consistent with the law to minimize the unwarranted economic and regulatory burden of the act, and prepare to afford the states more flexibility and control to create a more free and open healthcare market.”

The Anthem and Aetna cases were two of the biggest antitrust actions in Washington in years, and they highlighted an aggressive regulatory and enforcement response to what top Obama lawyers described as a “merger wave” among big companies.

U.S. District Judge Amy Berman Jackson, presiding over the Anthem trial, hasn’t yet issued a ruling. A decision is expected soon.

The ruling Monday came as the Trump administration sets up new leadership in the Justice Department and the Federal Trade Commission, potentially presenting a new dynamic for companies after eight years of Democratic-led regulatory and enforcement agencies.

Some Trump advisors have argued that big doesn’t necessarily mean bad. Still, Trump hasn’t given a clear sign about how his administration will approach corporate mergers. Trump has repeatedly said he’s not in favor of AT&T Inc.’s proposed tie-up with Time Warner Inc.

"I have been on the record in the past of saying it's too big and we have to keep competition,” Trump told Axios. “So, but other than that, I haven't, you know, I haven't seen any of the facts, yet. I'm sure that will be presented to me and to the people within government."

In a press release from the DOJ, Deputy Assistant Attorney General Brent Snyder, who is currently heading the Justice Department’s Antitrust Division, said, “Today’s decision is a victory for American consumers – especially seniors and working families and individuals. Competition spurs health insurers to offer higher quality and more affordable health insurance to seniors who choose Medicare Advantage plans and to low-income families and individuals who purchase insurance from public exchanges. This merger would have stifled competition and led to higher prices and lower quality health insurance. Aetna attempted to buy a formidable rival, Humana, instead of competing independently to win customers. Millions of consumers have benefited from competition between Aetna and Humana, and will continue to benefit because of today’s decision to block this merger."