In his ruling, Suffolk County Superior Court Judge

Kenneth W. Salinger

didn’t rule on the validity of the state’s fiduciary rule, which requires brokers to act in their clients’ best interest. Instead, he indicated Robinhood could continue to challenge the rule in court.

Robinhood has argued that the fiduciary rule doesn’t apply to the company, in part, because it is a self-directed brokerage that doesn’t make investment recommendations or provide advice. The brokerage has also argued that the rule is in conflict with other regulations and determinations, and that the state’s top securities regulator, Secretary of the Commonwealth

William Galvin,

is unable to “redefine the common law of broker-dealers.” The fiduciary rule was supported by Mr. Galvin and took effect last year.

In the decision, Judge Salinger requested further information from both parties about whether Robinhood’s challenge to the fiduciary rule should move forward, or whether it should be paused pending the outcome of state regulators’ administrative complaint.

Mr. Galvin’s office in December filed a complaint against Robinhood, alleging the company aggressively marketed to inexperienced investors and failed to implement controls to protect them. His office in April also asked that the company’s registration as a broker-dealer in the state be revoked to prevent Robinhood from doing business there. Mr. Galvin’s allegations were filed as an administrative complaint instead of in court, meaning that the case will be handled by a hearing officer.

In allowing securities regulators’ administrative complaint to go forward, Judge Salinger noted that state securities regulators’ complaint against Robinhood included allegations of violations outside the fiduciary rule, and that it would “not be in the public interest” to enjoin prosecution of the other claims.

Debra O’Malley,

a spokeswoman for Mr. Galvin, said in an email he was “pleased with this victory.”

Robinhood spokeswoman Jacqueline Ortiz Ramsay said in a statement that the company was “pleased that the court will address” the state’s fiduciary rule.

“We stand behind our customers, and we look forward to continuing to democratize finance for all in Massachusetts and across the country,” she said.

The online brokerage has previously disputed state regulators’ allegations, countering that it has opened the door to investing to millions of people. Robinhood had about 20 million users at the end of 2020, the Journal previously reported.

A decision regarding Massachusetts’ fiduciary rule could have broad implications for the brokerage industry. In an amicus brief filed this month, the Securities Industry and Financial Markets Association, a trade association, argued that allowing it to stand could reduce the ability for broker-dealers to “predictably operate” in the state, adding that companies will likely provide less information to investors on their platforms, fearing that “providing such information will subject them” to the fiduciary rule.

Write to Caitlin McCabe at caitlin.mccabe@wsj.com