The American Civil Liberties Union (ACLU) is suing Wal-Mart in Michigan after the company terminated an employee for medical marijuana use, CNN reported June 29.

Joseph Casias, a cancer patient and one of Michigan’s 20,000 approved medical-marijuana users, was fired in November 2009 after failing an on-the-job, injury-related drug test. He had been employed by Wal-Mart for almost five years, promoted once, and named Associate of the Year in 2008. He only used medical marijuana in his off-hours, he said.

“Wal-Mart made him pay a stiff and unfair price for his medicine,” said Scott Michelman, staff attorney with the ACLU Drug Law Reform Project. Wal-Mart officials said the company defers to federal standards in cases where the law is unclear.

Michigan is an at-will employment state, where workers can be fired for any reason except those covered under federal statute (such as race, gender, and religion); the ACLU is arguing that firing Casias constituted medical discrimination.