(NVR) - Napa County Supervisors will ring in the New Year with the old topic of possible rule changes governing winery growth.

On Tuesday, they’ll continue a discussion they began on Dec. 8. One issue that could become clearer is how the rights of existing wineries would be protected.

The county’s Agricultural Protection Advisory Committee recommended that new rules apply only to proposed wineries. That’s the only way this diverse, 17-person group could muster the needed two-thirds vote for its proposed package of winery rule changes.

County officials have since said that legally, any new use permit rules must also apply to expansions and major modifications at existing wineries. But, they stressed, new rules wouldn’t apply to rights that existing wineries already have.

A report by Planning, Building and Environmental Services Director David Morrison gives an example. He mentioned the proposed rule that new wineries on parcels of fewer than 40 acres couldn’t pave over more than 20 percent of the land for a winery, home and other uses.

An existing winery that already exceeds this development cap couldn’t expand any further beyond it, Morrison wrote. But neither would it have to remove structures to come into compliance with the new rule.

“There would be no ‘clawing back’ of existing, legally developed uses and rights,” Morrison wrote.

Recognition of existing rights has been a key issue for wineries. Attorney Richard Mendelson addressed the Board on behalf of Napa Valley Vintners at the Dec. 8 meeting.

Mendelson asked for a clear county statement recognizing existing winery uses as vested rights that are legal and conforming and that cannot be rescinded, revoked or traded away. He asked that wineries’ existing rights not hamper the wineries’ ability to adapt and expand operations.

What remains to be seen is whether all parties can agree that their concerns have been met.

Another question is whether any new rules would apply to pending winery applications and under what circumstances. A county report said the Board of Supervisors has discretion in this matter.