The legal challenge was made on Tuesday by two state farmers after their original lawsuit to end the US Drug Enforcement Administration's (DEA) ban on growing industrial hemp was dismissed. The ban began when the DEA moved for a motion to dismiss state law allowing the growing of industrial hemp under licence. DEA argued that industrial hemp at some point contains psychoactive levels of tetrahydrocannabinol (THC-). THC is listed as a controlled substance under the Controlled Substance Act (CSA). Hemp seed contains some 25 percent protein, making it second only to soybean for protein content. The seed is also said to be high in essential fatty acids such as omega-3. Meanwhile, firms in Canada - where commercial hemp can be grown - have been cashing in on its healthy content. Manufacturer Manitoba Harvest is just one example of this. Last year it added a hemp milk to its range of hemp food products. While hemp foods became legal in the US in 2001, production of the seed is still illegal, thereby stimulating Canadian production of the seed. About 90 percent of Canada's hemp products are destined for the US, according to Agriculture and Agri-food Canada. Legal battle Farmers Dave Monson and Wayne Hague are appealing against the dismissal of their first lawsuit by a district court in November. The road to the high court appeal began in 2005, when the North Dakota Legislative Assembly passed a law allowing people within the state to plant, grow, harvest and sell industrial hemp providing they obtain a licence. The industrial hemp covered should have no more than three tenths of one percent of THC. Monson, who is a member of the House of Representatives had planned to plant industrial hemp in order to remove the seeds and press them into oil to sell, or sell sterilized seed to customers. Hague had also wanted to supply other farmers with industrial hemp seed. In January 2007 they applied to the North Dakota Commissioner of Agriculture for licenses. They were granted licenses but were told they would not be effective unless they were registered with the DEA. In turn the DEA refused to grant licences. In June last year the farmers launched a legal bid at a district court for a judgment that their plans to cultivate hemp would not violate the CSA. They lost in November. Fair ground Hemp advocacy group, Vote Hemp, has said there is no need for the DEA to ban the right to grow industrial hemp. President Eric Steenstra said: "This appeal is basically saying why can Canadian farmers grow non-drug industrial hemp plants to produce perfectly legal hemp fiber and seed commodities for the interstate US market, but North Dakota farmers cannot under North Dakota's state-regulated industrial hemp program. "The DEA has banned hemp farming for 50 years by conflating hemp and marijuana on very shaky legal ground while at the same time imports of hemp fiber, seed and oil are allowed. With North Dakota regulating industrial hemp, there is no reasonable threat farmers would be able to grow marijuana without being caught."