Big Business Groups Just Sued the Government for Blocking the Pfizer-Allergan Merger by Jen Wieczner @FortuneMagazine August 4, 2016, 6:21 PM EDT E-mail Tweet Facebook Linkedin Share icons Two business groups representing Pfizer and Allergan are suing the government, claiming that its new regulations were “tailored to destroy” a planned merger between the pharmaceutical companies. The rules, issued in April by the Treasury Department and the Internal Revenue Service, significantly limited U.S. corporations’ ability to lower their tax rate by acquiring companies overseas in so-called “inversion” deals. Pfizer and Allergan called off their $160 billion deal less than 48 hours later, citing the disappearance of tax benefits under the new rules. On Thursday, the U.S. Chamber of Commerce in conjunction with the Texas Association of Business filed a lawsuit accusing the IRS and Treasury of abusing their power to “gerrymander a regulation to support rejection of the Pfizer inversion.” Both Pfizer pfe and Allergan agn are members of the Chamber as well as TAB (Allergan is represented indirectly by the latter, as it belongs to a subgroup of TAB). The Chamber says it is bringing the lawsuit, filed in a Texas federal court, on behalf of its “entire membership,” but Pfizer and Allergan are the only alleged victims the suit mentions by name. Rather than seeking monetary damages, the groups are asking the court to nullify the regulation known as the “Multiple Acquisition Rule,” which disregards any foreign company’s acquisitions of U.S. companies in the past three years when determining its stock ownership of the combined company. The rule meant that Allergan, which moved its headquarters from the U.S. to Ireland over the course of a flurry of deals, would have, in the eyes of the government, owned too small a share to lend the new company its lower tax rate. “As intended, the Multiple Acquisition Rule caused the two corporations to abandon their proposed merger,” the lawsuit claims. “Allergan and Pfizer were injured by the Multiple Acquisition Rule’s disruption of their merger plans,” it further alleges. The rule harms the companies, according to the legal complaint, by imposing “a regulatory disability” on the drugmakers’ ability to do M&A deals and “foreclosing merger opportunities. ” Neither Allergan nor the IRS responded to requests for comment. A Pfizer spokesperson said the company was not a party to the litigation, and therefore declined to comment. But she referred back to Pfizer CEO Ian Read’s Wall Street Journal editorial, published the same day the Allergan deal failed, in which he makes the same arguments echoed in the lawsuit. “While the Treasury’s proposal is a shot at Pfizer and Allergan, this unilateral action will hurt other companies as well,” Read wrote.