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Three women become choked up as they deliver news in a video posted to social media. “We did it, everybody,” says Leslie Manookian, the woman in the middle. She is a driving force in a campaign that has chipped away at the foundations of modern public health in Idaho. The group had just gotten lawmakers to pass what she called the first true “medical freedom” bill in the nation. “It’s literally landmark,” Manookian said. “It is changing everything.”

With Manookian in the video are two of her allies, the leaders of Health Freedom Idaho. It was April 4, hours after the governor signed the Idaho Medical Freedom Act into law.

The act makes it illegal for state and local governments, private businesses, employers, schools and daycares to require anyone to take a vaccine or receive any other “medical intervention.”

Whether the law will actually alter day-to-day life in Idaho is an open question, because Idaho already made it easy to get around the few existing vaccination requirements.

But it could have a significant effect in other states, where rules aren’t already so relaxed. And it comes at a time when diseases once eradicated from the U.S. through vaccination are making a resurgence.

The law runs against one of the hallmarks of modern public health: that a person’s full participation in society depends on their willingness to follow certain rules. (Want to send your child to public school? They’ll need a measles vaccine. Want to work in a retirement community during flu season? You might have to wear a mask.)

The new Idaho law flips that on its head. It not only removes the obligation to follow such rules, it makes the rules themselves illegal.

The new law sets Idaho apart from even conservative-leaning South Carolina, where two schools recently quarantined more than 150 unvaccinated children after measles arrived.

A person can spread measles for four days before symptoms appear. During the South Carolina schools’ quarantine, five students began to show symptoms, but the quarantine kept them from spreading it, the health department said this month.

That precaution would now be illegal in Idaho.

Idaho’s law caught the attention of people who share Manookian’s belief that — contrary to hundreds of years of public health evidence and rigorous regulation in the U.S.