The Council on American-Islamic Relations, the nation's most prominent Muslim civil rights group, is resisting an effort by the Service Employees International Union to organize its staff.

The National Labor Relations Board, the main federal labor law enforcement agency, has set April 24 as the date for the workers' election.

CAIR has argued before the board that it is a religious organization and therefore exempt from the National Labor Relations Act. A regional administrator for the labor board rejected that argument in a ruling Friday.

While CAIR is well-known for its aggressive efforts to target anti-Muslim bias, NLRB regional director Charles Posner said that the organization was not sufficiently religious to make it exempt from the labor act. He described it as "more akin to a secular civil rights group" and, therefore, its workers are covered by the act.

"The evidence establishes that the employer is not an organization that exists to propagate a religious faith, but rather is engaged in a commercial-type activity," Posner said.

"This is a great opportunity for CAIR," said Christopher Honey, communications director for the Maryland-based SEIU Local 500, which started the bid to represent CAIR's staff. "Like other similar groups, CAIR's staffers should have an opportunity to have representation."

Honey added that SEIU hopes that CAIR will not oppose the organizing effort any further and instead let the election go forward. CAIR could appeal the decision to the full board.

It is not clear how many people are employed by CAIR, which has a Washington headquarters and 30 regional chapters. Honey said the effort involved only the workers at the Washington headquarters and that the number there was "less than 50." SEIU is "confident" that it has majority support, Honey added.

The situation places the leadership of CAIR in an awkward position. It generally has allied itself with other liberal groups, but appealing Friday's decision would open it up to charges of being anti-union. Not challenging it means accepting that it is not covered by some federal religious exemption laws.

CAIR did not respond to a request for comment.

This is not the first time SEIU Local 500 has bid to represent the staff of a well-known liberal advocacy group. In 2014, it bid to represent the staff of Media Matters for America. Media Matters' leadership initially resisted the effort but eventually agreed to let the union represent its staff.