From a press release reprinted here:

Dr. John C. Eastman, director of the Claremont Institute's Center for Constitutional Jurisprudence, will be filing a civil complaint in the Los Angeles Superior Court this afternoon challenging the removal of the cross from the Los Angeles County Seal. The civil suit, styled David Horowitz et al. v. County of Los Angeles, et al., alleges that the County's decision to remove the cross is an illegal waste of taxpayer funds and violates the "No Preference" Clause of the California Constitution and the Establishment Clause of the United States Constitution...

Also named in the complaint as defendants are Los Angeles County Supervisors Yvonne Burke, Gloria Molina, and Zev Yaroslovsky, who voted to remove the cross from the County Seal...

UPDATE: The press release is here.

UPDATE 2: The AP report has a little additional background, but most of its information is already in the press release.