It's introduced today by a bipartisan group of Congresscritters on behalf of rent-seekers in the organic foods industry and anti-science mystificationists posing as consumer activists. Unfortunately, as the press release from Sen. Barbara Boxer (D-Calif.) notes, polls show that most Americans, spooked by anti-technology activist and organic commercial interest scare campaigns, want foods containing ingredients derived from biotech crops (nearly anything containing corn or soy) labeled.
The legislation would evidently force the Food and Drug Administration to mandate such labels even though the agency has heretofore only required labeling for science-based nutritional and safety information. To see why this legislation is a particularly egregrious abuse of science, see my article, "The Top Five Lies About Biotech Crops."
Frankly, ignorance looks like it's going to win, so food companies should just go ahead and slap labels on everything they sell reporting: "This product may contain ingredients derived from safe modern biotechnology."
For more background on why this labeling campaign traduces science to further what is just scaremongering for money and political power, see my article, "California Initiative Puts Profits Ahead of Science."