With Congress hurtling toward a possible government shutdown Friday night, a law protecting medical marijuana users could go up in smoke.

A 3-year-old law that blocks federal drug agents from going after medical marijuana businesses also has to be renewed.

If it isn't, Attorney General Jeff Sessions could sic Drug Enforcement Administration agents on medical marijuana dispensaries or growers around the country, including Arizona.

Sessions has hinted he might crack down on legalized marijuana nationwide.

Since winning voters' approval seven years ago, Arizona's medical marijuana business has boomed: 104 Arizona dispensaries serve 147,000 cardholders who spend an estimated $275 million a year on medical marijuana and related products.

Marijuana has become a more valuable cash crop in Arizona than cotton, one of the state's so-called "Five C's," the drivers of Arizona's economy at statehood 105 years ago.