Walmart fires employee with inoperable brain tumor for legally using marijuana outside of work

At his doctor's recommendation, Casias says he legally uses medical marijuana to ease his pain.

"It helps tremendously," he says. "I only use it to stop the pain. To make me feel more comfortable and active as a person."

During his five years at WalMart, Casias says he went to work every day, determined to be the best.

"I gave them everything," he says. "110 percent every day. Anything they asked me to do I did. More than they asked me to do. 12 to 14 hours a day."

But last November, Casias sprained his knee at work. Marijuana was detected in his system during the routine drug screening that follows all workplace injuries. Casias showed WalMart managers his state medical marijuana card, but he was fired anyway.