Seven states and the District of Columbia have filed a lawsuit against the Securities and Exchange Commission in an effort to block the regulator’s recently approved Regulation Best Interest (Reg BI) rule package.

The lawsuit, filed Monday in the U.S. District Court in the Southern District of New York, is being brought by the attorneys general of New York, California, Connecticut, Delaware, Maine, New Mexico, and Oregon, in addition to Washington D.C. It contends Reg BI “undermines critical consumer protections for retail investors, increases confusion about the standards of conduct that apply when investors receive recommendations and advice from broker-dealers or investment advisers, makes it easier for brokers to market themselves as trusted advisers (while nonetheless permitting them to engage in harmful conflicts of interest that siphon investors’ hard-earned savings), and contradicts Congress’s express direction.”

“With this rule, the SEC is choosing Wall Street over Main Street,” New York Attorney General Letitia James said in a statement. “Instead of adopting the investor protections of Dodd-Frank, this watered-down rule puts brokers first. The SEC is now promulgating a rule that fails to address the confusion felt by consumers and fails to remedy the conflicting advice that motivated Congress to act in the first place.”

Reg BI, approved as part of a package by the SEC in June, is set to be implemented by June 30, 2020. The rule is intended to enhance the quality and transparency of retail investors’ relationships with investment advisers and broker-dealers, bringing the legal requirements and mandated disclosures in line with reasonable investor expectations while preserving access (in terms of choice and cost) to a variety of investment services and products.

Under Reg BI, broker-dealers will be required “to act in the best interest of a retail customer” when making a recommendation of any securities transaction or investment strategy involving securities to a retail customer. It is designed to enhance the broker-dealer standard of conduct beyond existing suitability obligations and make it clear that a broker-dealer may not put their financial interests ahead of the interests of a retail customer when making recommendations.

However, the rule has stirred up controversy, with attorneys general pushing back on it even before it was approved. Shortly after passing the SEC’s vote, Democrats in the House of Representatives in late June passed legislation in attempt to starve Reg BI of funding.

SEC Chair Jay Clayton has vehemently defended the rule, citing a “lack of understanding of the law and legal obligations of financial professionals” shown in the negative commentary.

“I believe that much of this criticism—which is focused broadly on the extent of the investor protections under Reg. BI and our Fiduciary Interpretation—is false, misleading, misguided, and unfortunately, in some cases, is simply policy preferences disguised as legal critiques,” Clayton said during a July address at Babson College.