Imagine that you’re a small business owner getting ready to go into your busy season, when several protestors come onto your property and begin disrupting your workers. Ordinarily, you would call the police and have the trespassers removed so that you could continue with your operations. But in California, that’s not an option for some property owners.

Cedar Point Nursery—a strawberry farm near the Oregon border—didn’t have to imagine that scenario. In fall 2015, union protesters entered Cedar Point’s property at five o’clock in the morning, moving through trim sheds—where hundreds of employees were preparing strawberry plants during the final stage of the six-week harvesting season—with bullhorns, distracting and intimidating its workers.

This is where you would think you could appeal to the authorities to have unwanted visitors removed, but in 1975, California’s Agricultural Relations Board (ALRB) promulgated a regulation that promotes trespassing! This law—known as the “Access Regulation”—grants a right of access by union organizers to the premises of an agricultural employer for up to three hours a day and 120 days a year. In other words, California has granted an easement for unions to enter onto private property, extinguishing the owner’s right to exclude others.

The Fourth Amendment, however, protects private businesses (and everyone else) from such an invasion of their property rights. Indeed, the Fourth Amendment was drafted as a bulwark against the rampant government oppressions—invasions of people’s houses and businesses without a warrant—that existed before the Founding. The right to exclude was a fundamental aspect of the protection of property at common law, and has continued to be recognized as such throughout our nation’s history. Yet the Access Regulation essentially deputizes trespassers who, through their disruptive presence, are allowed to seize private property.

Cedar Point brought a civil rights suit against the ALRB and United Farm Workers, but the district court ignored the importance of property rights in determining whether the Fourth Amendment was implicated and upheld the law. Cato has now filed an amicus brief in the U.S. Court of Appeals for the Ninth Circuit, supporting Cedar Point and other property owners and asking that the district court be reversed.

California’s Access Regulation granted outsiders a gratuitous easement and extinguished the important right to exclude others, thus creating a classic seizure of property that violates the Fourth Amendment.