In upholding the lower court's decision in 2016, the unanimous panel of appellate judges found that Labor did give adequate notice that it was considering moving FIAs under a new prohibited transaction exemption.

Labor decided to regulate FIAs more strictly "because of their risk, complexity, and conflicts of interest," the 10th Circuit said in its ruling. "It did so with evidentiary support in the record. It is not this court's role to displace the agency's choice between two fairly conflicting views."

Where is the 5th Circuit's decision?

That the 10th Circuit upheld the Market Synergies ruling was not surprising, two ERISA attorneys told BenefitsPRO.

"Overturning an agency's adoption of a formal regulation is always a tough row to hoe," said Pat DiCarlo, an Atlanta-based partner in the law firm Alston & Bird. "The arguments for overturning the fiduciary rule as it applies to fixed indexed annuities were not particularly compelling."

If there was anything surprising to the 10th Circuit's decision, it was that it came before the 5th Circuit Court of Appeals' decision in a wider-ranging lawsuit brought against the Labor Department by the U.S. Chamber of Commerce and a consortium of financial services and insurance industry interest groups.

"Oral arguments in the 5th Circuit case were held a few months earlier than the 10th Circuit case," noted Kevin Walsh, an ERISA attorney with the Groom Law Group in Washington D.C.

In 2016, a Texas District Court upheld the fiduciary rule in the claim brought by the Chamber of Commerce. The 5th Circuit—regarded as one of the most business-friendly of the appellate courts—heard the Chamber's appeal last August.

The hearing was dominated by questions from a President Reagan-appointed judge that was openly hostile to how the Labor Department imposed new regulations on IRAs.

"The Department of Labor is labor—that's supposed to be employment relationships," said Judge Edith H. Jones during the hearing. "How does the Department of Labor have any expertise whatsoever in the market for individual investor advice?"

The 5th Circuit is regarded as the best chance opponents of the fiduciary rule have to overturn it via the courts. A decision was expected as early as last September, but the court has been silent.

That has left some to speculate that the 5th Circuit won't issue a ruling at all, or at least not until the Labor Department completes a review of and potential revisions to rule, ordered by President Trump.

"We still expect a decision from the 5th Circuit," said Mr. Walsh.

While it is possible the court could rule any day, Walsh pointed to two prevailing theories on how the court may be thinking in delaying its ruling.

"Some have speculated the 5th Circuit is hoping DOL will simply revise or pull back the rule itself, and that the case before the court would become moot. The other theory, and one I buy into more, is that the 5th Circuit is waiting for the Supreme Court to decide Murphy Oil, and that we'll hear from the appellate court shortly after that ruling," explained Mr. Walsh.

The Supreme Court heard arguments in NLRB v. Murphy Oil USA last October. That case, brought under the Federal Arbitration Act, questions whether regulators can prohibit class-action waivers in commercial contracts. The Labor Department's fiduciary rule includes a prohibition on class-action waivers, a question the 5th Circuit is considering in the Chamber of Commerce's appeal.

Careful what you wish for

Part of the fiduciary rule was implemented in June of 2017. The more technical warranty and disclosure requirements have been delayed until July of 2019 under the Trump administration.

Ultimately, the 5th Circuit will have to issue a decision, but is not under any deadline, said Mr. DiCarlo. "It is entirely possible the court is waiting for revisions to the rule before ruling."

The impartial conduct standards—the part of the rule that has already been implemented—require all advice on qualified retirement accounts to be in investors' best interest.

The 5th Circuit could vacate the impartial conduct standards, said Mr. Walsh. "The entire regulatory package is before the court. Whether a provision has been implemented doesn't matter. The court could do anything from striking down the entire rule, to striking down parts of the rule, to reforming parts of the rule, to affirming the District Court and leaving the entire rule in place."

For the most ardent opponents of the fiduciary rule, vacating the impartial conduct standards would be welcomed. But Mr. Walsh cautions that could open a Pandora's Box.

To date, five states are in the process of promulgating their own fiduciary standards. In Massachusetts, state regulators have brought an administrative action against Scottrade Inc., alleging that firm's failure to comply with Labor's fiduciary rule amounts to a breach of state ethics standards.

"There really is the potential for a 'be careful what you wish for' moment," said Mr. Walsh, referring to the possibility of the 5th Circuit striking down all or parts of the fiduciary rule.

"Right now, states have indicated that one of the reasons they are acting is that they are concerned that DOL will make changes to the fiduciary rule.  If the 5th Circuit vacates the rule in its entirety or strikes down major portions, there is an increased likelihood that states will get into the fiduciary rule-making game," added Walsh.