The Labor Department on Tuesday won a case in federal court brought against its fiduciary rule by Market Synergy Group, an insurance distributor.

The U.S. Court of Appeals for the 10th Circuit ruled that Labor did not "arbitrarily treat fixed indexed annuities differently from fixed annuities" under its final fiduciary rule.

Kansas-based Market Synergy Group (MSG) had argued that Labor threw FIAs under the fiduciary rule's best-interest contract exemption, or BICE, at the last minute.

"According to MSG, the DOL simply did not give notice that it might exclude FIAs from PTE 84-24 and therefore did not give adequate notice of the final rule," the ruling states. "We are unpersuaded. The [notice of public comment and review] clearly asks for comment on whether removing variable annuities from PTE 84- 24 but leaving FIAs and fixed rate annuities struck the appropriate balance."

The court's ruling found that Labor's decision to include FIAs under PTE 84/24 was "not arbitrary or capricious."

The decision "is another victory for every American trying  to save for a safe and secure retirement," said Stephen Hall, legal director and securities specialist for Better Markets. "The decision will help ensure that millions of Americans will not be swindled out of billions of dollars every year at the hands of financial advisors seeking to boost their profits and bonuses by recommending overpriced, underperforming and high-risk investments for retirement savers."

Soon after Labor finalized its rule "laying down the common-sense principle that all advisors to retirement savers must act in the best interest of their clients, industry opponents rushed into court with a slew of lawsuits," Hall said.

Leading the charge, Hall added, "were insurance agencies like Market Synergy who specialize in distributing complex investment products known as 'fixed indexed annuities,' or 'FIAs,' which generate huge revenues for the insurance industry."

Micah Hauptman, financial services counsel for the Consumer Federation of America, said the Tuesday decision "is yet another [one] concluding that the DOL acted properly in promulgating the rule. The DOL's careful analysis in promulgating the rule stands in stark contrast to the agency's more recent arbitrary and capricious actions in delaying the rule's full implementation."