The Justice Department is getting involved in a lawsuit against the city's board of elections over its removal of more than 117,000 voters from its registration rolls last year.

This issue cropped up after the presidential primary in April last year. A number of Brooklyn voters showed up at the polls on primary day and learned that they were not registered to vote.

It turned out that the city's board of elections had thrown more than 117,000 registered voters off the voter rolls before the primary.

For the first time, the Justice Department says the action was illegal, a violation of the National Voter Registration Act.

A spokeswoman for the board of elections says the board does not comment on pending litigation.

Common Cause New York, a government watchdog group, sued the board over the issue last year, and has argued that the board illegally tossed these voters because they had not come out to vote in previous elections.

"It's a clear endorsement of the action we've taken to draw attention to the fact that the board of elections is not following federal law," said Susan Lerner of Common Cause New York.

After the removal of the voters was first reported by WNYC, the board of elections reversed course and reinstated them.

Thursday, the Justice Department filed a motion in federal court to intervene in the lawsuit and said it is concerned about how the board oversees its voter lists.

The Justice Department says it is worried that without changes, the agency's problems could lead to additional violations of the National Voter Registration Act.

"The right of citizens to vote is a critical part of democratic process," said U.S. Attorney Robert Capers of the Eastern District of New York. "We will work tirelessly to ensure that, in the future, the New York City Board of Elections fulfills its statutory obligation to maintain the rolls properly, and follows the appropriate notice and timing requirements for voters that federal law requires when it does so."

For Lerner, the disappearing act is part of a bigger problem: the elections agency is controlled by the Democratic and Republican Parties, and there have long been calls reforms in the way the agency is staffed and run.

"The people who are chosen, in major part, are chosen for their political party affiliations, not for their experience in administering elections," Lerner said. "When you don't have a fully professionalized staff, you are going to have these kinds of problems."

The timing of this is of note; we are about a week away from Donald Trump being inaugurated as president and installing a new head of the Justice Department. It is possible that the head of the department's civil rights division and Capers wanted to get this in motion before that happens.

Meanwhile, the board of elections is talking about bringing back the old lever voting machines for the mayor's race this year.

There are some concerns that the agency would not have enough time to print ballots for the current machines in the event of a run-off.