Congress adopted country of origin labeling six years ago and it finally takes effect today. Too bad you still don't know where Spam comes from.Consumers overwhelmingly are in favor of the rules, which require labels on most foods that show where the food was raised — especially as tainted dairy products from China are being pulled from grocery store shelves worldwide. But not everyone is happy with the way the U.S. Department of Agriculture has implemented the rules. "USDA may be trying to dodge congressional intent,'' said Representative Rosa DeLauro of Connecticut, the Democrat who heads the House subcommittee that oversees the department's funding. For instance, mixed vegetables are exempt from the regs. So is mixed meat (i.e., Spam and other processed foods. The U.S. Cattlemen's Association and R-CALF object to regs that would allow packers to label beef as coming from "mixed" countries even if an animal was born, raised and slaughtered exclusively in the U.S.