Here's an FAQ from the FDA about GM-foods, that says "[f]oods from genetically engineered plants must meet the same requirements, including safety requirements, as foods from traditionally bred plants."
There is broad scientific consensus that food on the market derived from GM crops poses no greater risk than conventional food. No reports of ill effects have been documented in the human population from GM food.
http://www.genetics.org/content/188/1/11.long
http://www.sciencedirect.com/science/article/pii/S0306919210000254
http://www.nap.edu/catalog.php?record_id=10977#toc
http://jrs.sagepub.com/content/101/6/290
Also, here's a highlight from a court ruling in Vermont that I think is relevant:
Although the Court is sympathetic to the Vermont consumers who wish to know which products may derive from rBST-treated herds, their desire is insufficient to permit the State of Vermont to compel the dairy manufacturers to speak against their will. Were consumer interest alone sufficient, there is no end to the information that states could require manufacturers to disclose about their production methods. For instance, with respect to cattle, consumers might reasonably evince an interest in knowing which grains herds were fed, with which medicines they were treated, or the age at which they were slaughtered. Absent, however, some indication that this information bears on a reasonable concern for human health or safety or some other sufficiently substantial governmental concern, the manufacturers cannot be compelled to disclose it. Instead, those consumers interested in such information should exercise the power of their purses by buying products from manufacturers who voluntarily reveal it.