Perez said in a statement the same day, however, that DOL's rule is “built upon solid statutory and legal foundations, and we will defend it vigorously.” The ”handful of industry groups and lobbyists are suing for the right to put their own financial self-interests ahead of the best interests of their customers.”

DOL has 60 days to respond to the lawsuit.

The nine plaintiffs include the Securities Industry and Financial Markets Association, the Financial Services Institute, the Financial Services Roundtable, the U.S. Chamber of Commerce, the Insured Retirement Institute and four Texas groups, including the Texas Association of Business.

Ken Bentsen, president and CEO of SIFMA, noted on the call that while all of the trade groups represent members nationwide, about 27,000 advisors in Texas are registered with the Financial Industry Regulatory Authority and that Texas ranks third in the U.S. in terms of the number of advisors and fourth in the number of broker-dealers, which “underscores the fact that this is a Main Street issue.”

Scalia, who previously served as DOL's chief legal officer and is the son of the late Supreme Court Justice Antonin Scalia, agreed, stating that the DOL rule's impact “is nationwide, but it's very great in Texas. It's appropriate that [the lawsuit be filed] in a Main Street jurisdiction; it's not an inside the Beltway case.”

Scalia added that DOL “will have to decide how they want to move” on the case, which could mean seeking to change its venue, but added, “I don't know why they'd want to move it to someplace else.”

n separate comments to ThinkAdvisor, Scalia said that during his time as DOL solicitor, “I don't recall a case where we felt we needed to move” venues.

As to DOL's 60-day deadline to respond, Scalia said that “We expect to seek a means fairly promptly to be resolved in advance of the [April] compliance deadline.”

But Mercer Bullard, professor of law at the University of Mississippi Law School and founder of Fund Democracy, an advocacy group for mutual fund shareholders, told ThinkAdvisor on Thursday that “the plaintiffs have hurt their cause by delaying” filing a suit until now. ”Why should a court be sympathetic to their request to postpone the effective date when they waited so long to file and then filed where they know there will be a fight over removing the case to DC?”

The groups' ”actions undermine their argument that postponement is necessary,” Bullard continued. “It seems they're betting on the court from the country of Texas ruling for them strictly on political grounds.”

Bullard added that “the [fiduciary] issue is national; DOL in is DC, the real plaintiffs are based in DC, the faux Texas plaintiffs have no special Texas-interest.” Also, the parties to the suit are in Washington as are the “people who made” the DOL rule. “This is just blatant forum shopping.”

Scalia, who co-chairs his firm's Administrative Law and Regulatory Practice Group and is a member of its Labor and Employment Practice Group, said the lawsuit first challenges the “definition and meaning” of the word fiduciary.

“Fiduciary is a very familiar and important word in the legal lexicon,” Scalia said, “and DOL has given it a meaning that is unrecognizable. Our complaint begins with the overbroad definition of fiduciary.”

The suit also challenges DOL's oversight of IRAs as well as the rule's creation of a “private right of action” to bring class-action lawsuits under the best interest contract exemption, which Scalia called “one of the most troubling aspects” of BICE.

DOL's rule, the complaint states, and its prohibited transaction exemptions “overstep the department's authority, create unwarranted burdens and liabilities, undermine the interests of retirement savers and are contrary to law.”

The suit also states that DOL's fiduciary rule would “upend” the “well-developed regulatory framework” currently in place consisting of securities laws enforced by state and federal regulators, and that DOL's rule will have “harmful consequences for retirement savers, small businesses, and tens of thousands of businesses — including many operating in North Texas and the Dallas-Fort Worth metroplex — that provide retirement advice, products and services.”

Bentsen stated on the Thursday morning call that it is the Securities and Exchange Commission that was “authorized by Congress” to promulgate a fiduciary rule. DOL's rule “is not consistent with where Congress is at. We were left with no other choice than to pursue this action.”

Dale Brown, FSI's president and CEO, stated on the call that FSI, as well as the other groups joining the suit, “has supported a uniform fiduciary standard since 2009 – before Dodd-Frank became law … but the Department of Labor's complex and unworkable rule will only harm the smaller investors it claims to protect.”

This legal challenge, Brown continued, “is solely about ensuring the rules governing retirement advice work for all retirement investors. This [DOL] rule does not pass that test.”

Brown noted that while the lawsuit is a “necessary next step to seek relief,” FSI and other groups are nonetheless ”actively helping our members to comply with the rule.”

Barbara Roper, director of investor protection for the Consumer Federation of America, said that “it has been clear from the outset of this process that industry groups would challenge the DOL rule in court. After all, financial firms, such as those represented by these trade associations, are able to earn billions of dollars a year in excess profits under the current regulatory regime, money that comes directly from the hard-earned retirement savings of American workers and retirees.”

DOL's rule, she added, “goes to the heart of these anti-investor practices, so naturally firms that have profited handsomely under the current system find it threatening. Despite their oft-professed concern for low- and middle-income savers, it is those billions in excess profits that this lawsuit is intended to protect.”

The lawsuit states that DOL's rule “expands who is covered by the [fiduciary] term in a manner that is inconsistent with the statutory text and the ordinary and historical understanding of what constitutes a fiduciary relationship.”

In doing so, the complaint continues, DOL “bans common and long-accepted forms of compensation for financial services and insurance professionals, such as commissions and sales loads (a mutual fund sales charge). The Department's broad redefinition has this effect because fiduciaries under ERISA and the Code are prohibited from receiving compensation that varies based on the investment 'advice' provided or transaction engaged in.”

DOL, the complaint continues, “is well aware that these methods of compensation are essential for firms and professionals to continue to offer many of the valued services and products they provide.”

Second, DOL “then offers an exemption from this far-reaching prohibition — known as the best interest contract exemption (or “BIC” exemption) — but conditions it on financial services firms and insurance institutions agreeing to subject themselves to fiduciary standards of conduct in contracts that they must enter into with their customers, as well as a range of other restrictions and requirements.”

In short, the complaint says, DOL “is instituting a deliberately unworkable fiduciary definition, with full knowledge that financial services firms and insurance institutions will have no choice but to seek an exemption from it. The department is conditioning that exemption on an agreement to adhere to practices that the department has no authority to require or enforce, and that will therefore be administered instead by the class-action bar.”