I posted this question over at the Straight Dope.

Black and white flag at Tour de France

I've done some searching for this and can't find anything. At the Tour de France, which I watch every afternoon in July, I see fans waving flags in the pattern of the American flag, but with black and white stripes and what appear to be about twelve small pine trees on a white field. I've been seeing this for the past several years. As far as I know it's not a Basque or Catalan separatist flag, and as far as I know it doesn't represent any of the teams. I can't figure out what it means, and I see it several times every day. This is starting to get on my nerves. Please help.