Cocktails are mixed with great sincerity at Bourbon and Branch in San Francisco. Take the Clermont Affair, a marriage of pear-infused Old Overholt whiskey, a liqueur called Amaro Nonino, barrel-aged bitters and a house-made tincture of cloves.

The $12 drink, the menu reveals, "tells the story of a flawed love."

But for state liquor license regulators, the concoction itself is flawed. On a recent Friday night, they entered the speakeasy-themed Tenderloin tavern and warned bartenders they were breaking California law by altering alcohol - infusing it with the flavors of fruits, vegetables and spices.