Five national financial services trade groups filed suit against the Department of Labor’s fiduciary rule for retirement plan advisors Thursday, arguing that the DOL had exceeded its congressional authority.

At the same time, one of the associations, the Financial Services Institute, said it’s full speed ahead on compliance.

During a press conference announcing the suit, FSI President and CEO Dale Brown said his members were doing everything they can to be prepared to obey the rule when it is scheduled to start taking effect in April.

FSI was joined in the legal action by the Financial Services Roundtable, the U.S. Chamber of Commerce, the Securities Industry and Financial Markets Association and the Insured Retirement Institute.

Seeking a bar on the regulations, the suit warned that, “without an injunction, the rule and exemptions will impose myriad compliance costs on the financial services industry—costs which, according to the DOL’s own flawed estimate, are $5 billion in the first year—and lead some financial professionals and their companies to forgo or cease serving certain clients, and even to leave the business altogether.”

The suit also called the rule a violation of free speech rights.

“Under the First Amendment, financial institutions and financial professionals have a constitutional right to engage in truthful, non-misleading speech about products and services without the government imposing unreasonable or excessive burdens,” the trade groups said in the court filing.

But Labor Secretary Tom Perez claimed the suit was the work of a vocal minority trying to protect their interests above their clients’.

“The department’s conflict of interest rule is built upon solid statutory and legal foundations, and we will defend it vigorously,” Perez promised.

However, the suit contended that the Labor Department arbitrarily and capriciously assessed the benefits, consequences and costs of the rule.

Barbara Roper, the director of investor protection at the Consumer Federation of America, called the legal arguments in the suit “flimsy.” She added that while the trade groups claimed the suit was being filed to protect the ability of retail investors to receive financial advice, the underlying motive was to protect billions in excess profits.

Also objecting to the suit was the Financial Planning Coalition comprising the CFP Board, the Financial Planning Association and the National Association of Personal Financial Advisors.

The coalition warned the suit could negatively impact millions of retirement savers by delaying the start of the regulations.

The Investment Adviser Association issued a statement in support of the rule.

“While the DOL rule will require SEC-registered investment advisers to modify their policies, procedures and record-keeping with respect to retirement accounts, the rule will not fundamentally change the core fiduciary principles governing investment advisors’ service to their clients,” said IAA President and CEO Karen Barr.

SIFMA, FSI and other groups claimed the rule would hurt retail investors by increasing the cost and decreasing the availability of financial advice.

“The rule will shackle Main Street financial advisors with extensive new requirements and constant liability, forcing them to limit the options and guidance they provide to retirement savers,” the five trade groups said in a joint statement.

SIFMA President and CEO Ken Bentsen said the Securities and Exchange Commission should have gone first in establishing a uniform fiduciary duty for financial services providers.

The SEC is scheduled to publicly consider a uniform standard for investment advisors and broker-dealers the same month next year when the DOL’s best interest standard becomes operative. However, SEC timetables are often little more than loose aims, and a new chair is likely to be at the helm no matter which party wins the presidential election.

Leading the legal fight is Wall Street’s favorite lawyer in fighting federal regulation, Gene Scalia, the son of the late U.S. Supreme Court Justice Antonin Scalia.

In the Congress, Rep. Maxine Waters, the lead Democrat on the House Financial Services Committee, chastised the groups for filing the suit, contending they seek to block a much-needed and long overdue rule.

House Speaker Paul Ryan said the fiduciary rule would hurt non-profits, colleges and universities, start-ups and tech companies, young people and state and local governments the most.

The suit was filed in the U.S. District Court for the Northern District of Texas. Joining the national organizations in the legal action were the Greater Irving Las Colinas Chamber of Commerce, the Texas Association of Business, the Lake Houston Area Chamber of Commerce and the Lubbock Chamber of Commerce.