They told a federal court in Phoenix that forcing Loughner to take mind-altering psychotropic drugs is a violation of his rights, CNN reported Tuesday.
Loughner, 22, was transferred to the U.S. Medical Center for Federal Prisoners in Springfield, Mo., in late May to restore his mental competency.
He is charged in the mass shooting in Tucson last January in which six people were killed and 13 others wounded, including U.S. Rep. Gabrielle Giffords.
In her first public appearance since being wounded in the head, Giffords, D-Ariz., accompanied her husband, former astronaut Mark Kelly, who received a medal at an awards ceremony Monday evening at Space Center Houston.
Giffords' spokesman, C.J. Karamargin, said he was not surprised at all she attended the ceremony.
"For us it is clear that the congresswoman's physical strength is improving as well as her cognitive and verbal abilities," Karamargin said.