Groups challenging the constitutionality of Iowa’s so-called “ag gag” law said they received an important legal green light this week with a U.S. district court ruling that lets the lawsuit proceed.

A federal judge Tuesday denied Iowa’s motion to dismiss a lawsuit that claims the state’s ag gag law violates the First Amendment, protecting freedom of speech.

A coalition of public interest groups challenging the law called the ruling a big win.

The ag gag law “clearly is a violation of Iowans’ First Amendment rights to free speech,” said Rita Bettis, ACLU of Iowa’s legal director. “It has effectively silenced advocates and ensured that animal cruelty, unsafe food safety practices, environmental hazards and inhumane working conditions go unreported for years.”

The 2012 Agricultural Production Facility Fraud law makes it a crime for journalists and advocacy groups to go undercover at meatpacking plants, livestock confinements, puppy mills and other ag-related operations to investigate working conditions, animal welfare, food safety and environmental hazards, among other practices.

Eric Tabor, Iowa’s chief deputy attorney general, said it’s early in the case’s litigation and declined to comment further.

The American Civil Liberties Union of Iowa, along with the Animal Legal Defense Fund, Bailing Out Benji, Iowa Citizens for Community Improvement and others, filed the lawsuit last fall.

The Iowa law says people who lie to gain access or employment at a farm operation, with an intent to take action not authorized by the owner, could be charged with a serious misdemeanor, potentially carrying a year of jail time.

Additional violations are considered an aggravated misdemeanor, carrying up to two years of jail time.

Ron Birkenholz, a spokesman for the Iowa Pork Producers Association, said the law was drafted to “provide meaningful protection to farmers” while “respecting and protecting all citizens’ constitutional rights.”