I see this on more than a few cars in the US. What does this decal mean?
Most likely this decal represents the “thin blue line” of law enforcement between regular folks and criminals; however; I’ve also heard that there’s also a similar decal that stands for bear-related activities and/or SMDB. I’d side with the law enforcement explanation.
Not quite…the Leather Flag has blue and black (and white) stripes (plural), not one blue stripe on a black background. And the Bear Flag is shades of brown and gold.
Beaten to the punch. ::sigh::, I’m losing my touch in my older years.
I’ve been wondering for years what this thing meant. Thanks!
A friend was doing research in a rural area and became friendly with a local gas station owner. She finally asked him on day if he knew the rainbow flags he flew on the station everyday were a symbol of the gay rights movement. He said he didn’t know, but said he liked them and kept them up anyway. She said she was sure he wasn’t gay. I’ve often wondered how many rainbow flags are flying just for that reason. “Look, it’s so pretty.”
Whippersnapper… 
The rainbow is also the symbol of the Cursillo Movement, a cross-denominational thing in Christianity (started by Spanish Catholics, spread worldwide, picked up by Episcopalians and then by Methodists and UCC’ers among others) where a three-day short course (“cursillo”) in practical Christianity is followed by an ongoing commitment to a deeper spiritual life. In that program, it symbolizes “all the colors of God’s love.”
It’s worth noting, too, that the HRC equals-sign logo is not a symbol meaning “I’m gay” but rather “I support equal rights for gay people.” My wife and I had that decal on our car bumpers for years (haven’t picked a new one up for our current car).