Related: See more DOL fiduciary rule coverage

In its claim, NAFA argued DOL breached its statutory limitations under the Employee Retirement Income Security Act by redefining the term "fiduciary" and requiring advisors to IRAs to act as fiduciaries.

It also alleged DOL's rule creates a new private right of action by prohibiting class-action waivers in the Best Interest Contract Exemption, something only Congress has the authority to do.

NAFA also argued that the rule's "reasonable compensation" requirement is too vague, and that DOL violated the APA by failing to give industry adequate notice when it moved the treatment of fixed indexed annuities from Prohibited Transaction Exemption 84024 to the purview of the BIC Exemption.

Judge Moss detailed the shortcomings of NAFA's argument claim by claim in the ruling, which was close to 100 pages long.

In amending the five-part test used to determine fiduciary status prior to the new rule—specifically, the former requirement that investment advice be given on an on-going basis—the DOL acted within its statutory authority, according to the ruling.

Under the fiduciary rule, a new standard was created, whereby one-time transactions, like the sale of an annuity, will constitute a fiduciary act.

"Given changes in the retirement investment advice market since 1975, the Department reasonably concluded that limiting fiduciary status to those who render investment advice to a plan or IRA 'on a regular basis' risked leaving retirement investors inadequately protected—particularly when one-time transactions like rollovers will involve trillions of dollars over the next five years and can be among the most significant financial decisions investors will ever make," wrote Judge Moss in his decision.

Setting up a circuit split

Judge Moss' decision will come as little surprise to most ERISA and administrative law experts, says Erin Sweeney, an attorney with Miller and Chevalier.

"This is how we thought the D.C. court would rule," she said in an interview. "The D.C. district court has a history of being sympathetic to regulatory agencies, and the DOL in particular."

Like other experts tracking litigation against the rule, Sweeney surmises that the suit brought in the D.C. District was part of a larger estimation by NAFA and other stakeholders that an appellate split will ultimately emerge from the four lawsuits, prompting the Supreme Court to at least consider hearing the case.

Sweeney, who was in attendance for oral arguments in the NAFA case, characterized Judge Moss' line of questioning as "hostile" to NAFA.

She was also in attendance for oral arguments in Market Synergies Group, Inc. v. Department of Labor, heard in September in the U.S. District Court for the District of Kansas.

That case, brought on behalf of an independent marketing organization that distributes fixed indexed annuities through 3,000 independent insurance agents, makes claims similar to those raised in NAFA's lawsuit, and argues that the rule will cause irreparable harm to the fixed indexed annuity market by effectively dismantling how the products are now distributed.

Related: IMO makes targeted claim against DOL rulemaking procedures

Market Synergies' claim is being heard in a venue that is presumably more favorable to its interests. The Kansas court has issued previous injunctions against the DOL, said Sweeney. Judge Daniel Crabtree's line of questioning during oral arguments in that case was more hostile to DOL's line of argument, she said.

The timing of NAFA's appeal to the D.C. Circuit will be important. Sweeney expects NAFA to file for an expedited appeal. Under rules specific to the D.C. Circuit, parties are allowed to file motions to expedite an appeal.

D.C. Circuit documents indicate the court grants expedited appeals very rarely. Sweeney said the bar is high for expedited review—NAFA will have to demonstrate that its members will be subjected to "irreparable injury" if the Circuit's review is prolonged.

An appeal on a regular track could take up to a year-and-a-half before a decision is reached, said Sweeney. On the expedited track, a decision could be issued in a matter of months. The DOL rule's first implementation deadline is April 10, 2017.

Implications of summary judgment

NAFA has 30 days from Friday's decision to file a motion for expedited appeal.

Ultimately, Sweeney says an appellate decision is unlikely to overrule Judge Moss' decision.

But in denying NAFA's motion for preliminary injunction, and granting DOL's cross motion for summary judgment, Sweeney says the decision increased the possibility that a potential motion for expedited appeal would be granted.

A ruling on a preliminary injunction would have been a much more narrow decision than Moss' summary judgment ruling. In issuing a summary judgment, Moss effectively said the DOL was within its regulatory authority to make the fiduciary rule.

A preliminary injunction ruling would have addressed NAFA's more specific claim that its members have been irreparably harmed by the rule. That claim, denied by Moss, would have required regulators "to hit the pause button" and readdress the rule's implications for NAFA members, explained Sweeney.

Sweeney is confident that Moss' summary judgment in favor of DOL will open the door for an expedited appeal.

 "Frankly, I don't see where the court has a choice but to expedite the appeal in this case," said Sweeney. "I expect the appeal to move as quickly as possible."