Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

A federal judge in Washington, D.C. ruled Friday that Hillary Clinton must answer written questions from a group that filed a lawsuit over her private email server.

Lawyers for Judicial Watch, a conservative government watchdog organization, asked to interview her under oath as part of their Freedom of Information Act lawsuit against the State Department.

Related: Clinton Told FBI Colin Powell Recommended Private Email: Sources

But Judge Emmet Sullivan said Friday that the group "has failed to demonstrate that it cannot obtain the discovery it seeks through other, less burdensome or intrusive means such as interrogatories."

Hillary Clinton LUCAS JACKSON / Reuters

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

He gave the group until October 14 to give her the questions, and she has 30 days to answer them.

If the group wants to ask her follow-up questions in writing, it must go back to the judge and get permission.

The group is seeking the details of Huma Abedin's relationship with the State Department that permitted her to do outside work while she was a top aide to Secretary Clinton.

Judicial Watch lawyers told the judge that only by interviewing Clinton under oath could they hope to learn why set up up a private e-mail server.

Clinton's lawyers argued that because so much has previously been disclosed — through her testimony to Congress, the report of the State Department's inspector general, and the findings of the FBI — there was no need to depose her about the email server her in order to learn the details of Huma Abedin's contract.

Judicial Watch insisted that none of those other inquiries delved into why a private server was used in the first place.

"Secretary Clinton has never testified under oath why she created and used the clintonemail.com system to conduct official government business. Her only public statements on the issue are unsworn," the group's lawyers said in court filings.

In Friday's order, Judge Sullivan said her written testimony is necessary "to enable her to explain on the record the purpose for the creation and operation of the clintonemail.com system for State Department Business."

Despite all of her statements and congressional testimony, the judge said, she still hasn't explained why she set up the server.

Judicial Watch said in a statement Friday it is pleased with the ruling. "We will move quickly to get these answers," Judicial Watch President Tom Fitton said. "The decision is a reminder that Hillary Clinton is not above the law."

But Brian Fallon, spokesman for the Clinton campaign, said the Judicial Watch effort "is just another lawsuit intended to try to hurt Hillary Clinton's campaign, and so we are glad that the judge has accepted our offer to answer these questions in writing rather than grant Judicial Watch's request."