WASHINGTON — A federal judge opened the door to allowing a conservative legal group to question top aides to former Secretary of State Hillary Clinton about whether she deliberately sought to thwart open records laws by using a private email server.

U.S. District Court Judge Emmet G. Sullivan ruled Tuesday that Judicial Watch can prepare a plan for “narrowly tailored discovery” into the circumstances surrounding the Democratic presidential candidate’s use of a home-based email server during her stint as the nation’s top diplomat from 2009 to 2013.

The lawsuit stems from a Freedom of Information Act request seeking records related to the employment status of Huma Abedin, Clinton’s former deputy chief of staff. A longtime confidante, Abedin was allowed to work simultaneously for both the State Department and the Clintons’ private foundation. She is now vice chair of Clinton’s 2016 campaign organization.

Judicial Watch President Tom Fitton called Sullivan’s order “a major victory for the public’s right to know the truth about Hillary Clinton’s email system.”

The judge ordered Judicial Watch to submit its plan by March 15, the date of Democratic Party primaries in Florida, Ohio, North Carolina, Missouri and Illinois. The group said it will seek to depose under oath both current and former officials of the State Department, and potentially Clinton herself.

The case is one of dozens of pending civil lawsuits over issues surrounding Clinton’s emails. The FBI is also conducting an investigation into whether classified information passed through the home-based server.