A Sonoma County judge Tuesday sided with rock quarry opponents in a challenge over their free legal counsel.

In his tentative ruling, Judge Elliot Daum denied a motion from quarry owner John Barella to disqualify Morgan, Lewis & Brockius on grounds that the firm had represented Basin Street Properties, a real estate group in which Barella is the single largest investor.

Daum found that although Barella had spoken with a lawyer from the firm in 2009, he didn't personally retain him and didn't give the attorney any information that was related to the quarry case.

Also, Daum said the quarry would suffer no harm if the motion was denied but quarry opponents would because it is unlikely they will be able to retain another firm on a pro bono basis.

If oral argument is requested, it will be heard on June 8, Daum said.

Citizens Advocating for Roblar Rural Quality sued Barella and the county after the Board of Supervisors approved the 70-acre quarry in December.

The 200-member group claims it would harm water and air quality, increase traffic and hurt wildlife and nearby county-protected open space.

It claims an environmental review supporting the project did not sufficiently address the issues.

The lawsuit was combined with another suit filed by two local dairy families over a related habitat replacement deal on county-protected open space next to the quarry.

In his motion, Barella argued the quarry group was using a firm which represented Basin Street. He said it amounted to a betrayal of the attorney-client relationship.

As evidence, he cited a single meeting at Basin Street's Petaluma headquarters more than two years ago when Stephen Finn, a Morgan Lewis partner, allegedly provided legal advice on the restructuring of Barella's personal loans with Mechanics Bank.

Morgan Lewis responded that it never represented Barella and had no obligation to end its free work. The lead counsel, Michael Molland, lives about six miles from the quarry and was critical of the project as it made its way through the planning process.