(CBS SF) — Last Thursday, a state law was introduced that, if passed, will eliminate the “personal belief” exception to California’s vaccination law.

Right now, under California law there are two ways to get out of having a child vaccinated: one is if you have a medical reason, and two is if you have a “personal belief” that prevents vaccination. The law proposed last week would leave that medical exception in place and get rid of that “personal belief” part.

The lawmaker who authored the bill is State Senator Richard Pan, who is also a doctor. He’s concerned about the outbreak of measles in California since December and the high numbers of people opting out of vaccines using the personal belief exemption.

The law as it is written so far does not have any religious exemption. And one might not be required. According to a 1944 U.S. Supreme Court case, “the right to practice religion freely does not include liberty to expose the community or the child to communicable disease or the latter to ill health or death.” In fact, West Virginia and Mississippi do not have religious exemptions.

READ MORE: Could I Get The Measles As A Vaccinated Adult?

To be clear: the police don’t come to your house and check to make sure children are vaccinated. In California we find out about a child’s vaccination status when you try to enroll them in school.

Legally, you can’t enroll children in school without vaccinations or an exemption.

Editor’s Note: An earlier version of this article indicated that – even if the law passes – parents can get around the mandate by homeschooling children. According to the HomeSchool Association of California, state health and safety codes actually require that home-based private schools maintain documentation showing that each pupil has received the same required immunizations as those needed to attend public schools.

I believe that some version of the law will pass. It already has 26 sponsors, mostly Democrats, but 2 Republicans have also signed on. Politically, here’s what’s most important: for years there has been a small, vocal group of parents who oppose vaccination and there wasn’t a huge “pro-vaccination” outcry. But that has all changed. In recent months, there has been an uproar of pro-vaccine voters demanding higher rates of vaccination and and politicians are paying attention. It’s not just California, either – lawmakers in Washington and Oregon are considering closing some vaccine exemptions as well.

Here’s a timeline of the rise and fall of measles outbreaks and the role the anti-vaccine movement plays: