Mendocino County, California, was the first jurisdiction in the United States to ban the cultivation, production or distribution of genetically modified organisms (GMOs). The ordinance, entitled Measure H, was passed by referendum on March 2, 2004. Initiated by the group "GMO Free Mendocino", the campaign was a highly publicized grassroots effort by local farmers and environmental groups who contend that the potential risks of GMOs to human health and the ecosystem have not yet been fully understood. The measure was met with opposition by several interest groups representing the biotechnology industry, The California Plant Health Association (now the Western Plant Health Association) and CropLife America, a Washington-based consortium whose clients represent some of the largest food distributors in the nation, including Monsanto, DuPont and Dow Chemical. Since the enactment of the ordinance, Mendocino County has been added to an international list of "GMO free zones." Pre-emptive statutes banning local municipalities from such ordinances have now become widespread with adoption in sixteen states. Background GMOs are commonly considered to be any organism whose DNA has been modified by human intervention. Agricultural practices, however, have long used selective breeding techniques for the same purpose as modern biotechnology. Researchers now define genetically engineered organisms (GEOs) as those that are produced from a range of recombinant DNA technologies, which introduce a transgene into the genome of a host cell. The most widely practiced method involves the use of bacteria, which are able to penetrate the cell membrane of the host. Other methods include a "gene gun" or "biolistic particle delivery system". Recombinant DNA technology allows for the creation of synthetic genes with specific traits that have anthropogenic benefits. The term GEOs will be used here to describe organisms produced by the recombinant DNA technology commonly referred to by usage of the term GMOs. Environmental concerns The geographic and temporal scope of the regulatory debate regarding transgenic organisms and recombinant DNA technology is vast. Environmental risk assessments must weigh unquantifiable long-term risks against high and quantifiable short-term benefits. There is widespread concern amongst environmental groups, organic farmers and the international community that the introduction of transgenic organisms into local ecosystems may cause irreversible loss of biodiversity when the new synthetic strains become predominant. Further concern comes from members of the medical community who warn of the risk that the antibiotics used in the production of many GEOs may give rise to more resistant strains of