Lawmakers in Maine are considering a bill that would eliminate non-medical exemptions from vaccines.

If it passes the Senate, the bill would make Maine the the fourth state — following California, Mississippi and West Virginia — to ban all non-medical exemptions, including religious or philosophical ones. The move comes as the number of measles cases climbs nationwide, which has been attributed by experts to a "movement against vaccination in the U.S."

Medical ethicist Arthur Caplan said the bill could raise legal questions about the boundaries of the First Amendment and public health. Caplan is the Drs. William F. and Virginia Connolly Mitty Chair and director of the Division of Medical Ethics at NYU Langone Medical Center. He’s also the co-host of the "Everyday Ethics" podcast.

"There's a side issue about the constitutionality or the freedom to practice religion," Caplan told Boston Public Radio Wednesday.

He compared the exemption ban to a 1990 Supreme Court case which ruled that plaintiffs could not use an illegal drug, peyote, even though they maintained it was part of their religious practice.

Caplan pointed to the case as an example where religious freedoms were legally curtailed for what the court interpreted as the public good. He believes eliminating religious vaccine exemptions could meet the same threshold.

"You also can't use your religion as your basis to make other people sick. Religious freedom can be abridged," Caplan said.