The bus was stopped at the Border Patrol checkpoint in Sierra Blanca, east of El Paso, reports the El Paso Times. He posted bond and was released.
Nelson, 77, was headed from California to Austin, where he owns a ranch.
Nelson could face a minimum of six months in prison if convicted. Hudspeth County sheriff Arvin West told the El Paso Times that Nelson would be treated like any inmate if incarcerated in his jail.
"He could get 180 days in county jail, which if he does, I'm going to make him cook and clean," West said. "He can wear the stripy uniforms just like the other ones do."
TMZ.com reported that Nelson could argue that he forgot the marijuana was on the bus when he left California, where medical marijuana is legal.