Nine additional states have joined the U.S. Department of Justice and eight previous states in a lawsuit against Google LLC alleging that the search giant’s advertising business breaks antitrust law.

The lawsuit, first announced in January, charges that Google uses its position as a major provider of sell-side and buy-side advertising tools to harm market competition. Google is claimed to use its market position to raise the barriers to entry into the market to “artificially high levels,” leading rivals to exit the advertising technology industry and, in some cases, dissuading them from joining.

Arizona, Illinois, Michigan, Minnesota, Nebraska, New Hampshire, North Carolina, Washington and West Virginia have joined the lawsuit with California, Colorado, Connecticut, New Jersey, New York, Rhode Island, Tennessee and Virginia.

In a statement, the Department of Justice claimed that Google is monopolizing multiple digital advertising technology products in violation of Sections 1 and 2 of the Sherman Antitrust Act. The Sherman Antitrust Act prohibits monopolies and other anticompetitive practices that restrain trade or commerce. The 1890 act aims to promote competition and prevent businesses from engaging in practices that harm consumers or unfairly disadvantage competitors.

“We look forward to litigating this important case alongside our state law enforcement partners to end Google’s long-running monopoly in digital advertising technology markets,” Doha Mekki, principal deputy assistant attorney general of the Justice Department’s Antitrust Division, noted as the additional states joined the lawsuit.

Google spoke out against the lawsuit in January, claiming that the “DOJ is doubling down on a flawed argument that would slow innovation, raise advertising fees, and make it harder for thousands of small businesses and publishers to grow.”

The lawsuit, if entirely successful, would force Google to spin its sell-side advertising platform Google Ad Manager, which has its roots in Google’s purchase of DoubleClick Inc. in 2008. The lawsuit also seeks to force Google to divest the AdX auction platform, which brands use to bid for ad space and demands “any additional structural relief as needed to cure any anticompetitive harm” in the advertising technology market.

Photo: Google