After a year of speculation about how this administration's antitrust regulators would respond to deals between four of the five biggest health insurers — Anthem-Cigna and Aetna-Humana — the outcome is now clear.

The Department of Justice (DOJ) announced last Thursday that it will file lawsuits to stop the formation of what would be the two largest health insurance companies in American history.

Attorney General Loretta Lynch announced that the government would intervene because “These mergers would restrict competition for health insurance products sold in markets across the country and would give tremendous power over the nation’s health insurance industry to just three large companies.”

If the tie-ups went through, the five major private insurers in the nation would be reduced to just three and, Lynch said, “the competition among insurers that has pushed them to provide lower premiums, higher-quality care and better benefits would be eliminated.”

Combining Aetna and Humana, according to Bloomberg,would have created the largest provider in the private Medicare Advantage market, while the Anthem and Cigna consolidation would have formed the biggest insurer in terms of membership, mostly coming from services sold through employers.

The DOJ stated that these deals would raise health care costs and reduce choice for consumers. Coming at the same time, business and law experts said, the two deals stood out in the context of the administration’s antitrust policy, especially with regard to the health care industry. President Obama himself recently wrote an essay for the Journal of the American Medical Association promoting the need for competition to keep health care affordable for consumers.

In its complaint, the government said that the Anthem-Cigna deal would reduce competition in the market for commercial insurance from national employers as well as large-group employers in at least 35 metropolitan areas. The Aetna-Humana link-up would impact competition for at least 1.5 million customers in the Medical Advantage plans for the elderly, claimed the DOJ.

Critics of the proposed mergers had been resisting them since they were announced, resulting in pressures by consumer advocates and congressional hearings. Regulators in 12 states had given approvals, but as covered by the International Business Times, that process was tainted by ethics probes into regulatory reviews in Connecticut.

The DOJ decisions are consistent with actions against consolidations across industries, according to the Guardian, such as wireless companies AT&T and T-Mobile in 2011 and oil field servicers Halliburton and Baker Hughes this year. But concerns about safeguarding competition under the Affordable Care Act seem paramount, since a major aim of the law was to provide more insurance choices.

Government attorneys said that these companies “compete to sell health insurance on the public exchanges established by the Affordable Care Act” which “benefits low- and moderate-income individuals and families who buy insurance on the public exchanges. The merger would end this rivalry and deny consumers its benefits.”

The companies responded in differing ways. Aetna, Humana, Anthem vowed to contest the government’s lawsuit, while Cigna said that it was “evaluating its options” under the merger agreement. Litigation against the decisions could last months, said Bloomberg, further dragging out deals revealed about a year ago.

Antitrust law observers cited in The Guardian consider it unlikely that such large scale deals will be approved, “at least under this administration” — or a Clinton presidency, whose campaign “applauded” the DOJ decision — though none would guess how a Trump leadership would respond. In the shorter term, market watchers like Fortune expect Aetna, Anthem, Cigna, and Humana to go after smaller acquisitions and concentrate on what Aetna CEO called “organic growth” if these transactions fail.