Just because the 6th Circuit doesn't encompass Napa Valley doesn't mean it can't mediate spats between wineries. In Leelanau Wine Cellars, Ltd. v. Black & Red, Inc., No. 06-2391 (6th Cir. Sept. 20, 2007), the 6th Circuit confronted a claim that the winery name "Chateau de Leelanau Vineyard and Winery" infringed plaintiff's registration for LEELANAU CELLARS. Michigan's Leelanau Peninsula is a governmentally-approved American Viticultural Area (AVA).
While the 6th Circuit's review of the grant of summary judgment to the plaintiff was largely fact-intensive, it did not that the common element of the two marks (Leelanau) is geographically descriptive, and therefore weak, and this weakness was highlighted by the donning of AVA status to Leelanau Peninsula. The opinion also contained some useful discussion concerning factors that affect the admissibility and probative value of confusion surveys.