Calling the measure anti-Semitic, a threat to the religious freedom of both Jews and Muslims and an infringement on parental and medical rights, the plaintiffs are suing on the grounds state law prohibits local governments from restricting medical procedures, the Los Angeles Times reported Thursday.
An attorney for the group said male circumcision is safe, sanctioned and the most widely performed medical procedure in the country.
The ballot measure is a "distraction" to San Franciscans, parents, Jews, Muslims and doctors, attorney Michael Jacobs said.
The measure would prohibit what it calls the "genital cutting of male minors." Anyone who performed a circumcision would face a fine of up to $1,000 and up to a year in jail.
Lloyd Schofield, spokesman for the proposed measure, said his coalition was aware of the law prohibiting local governments from restricting medical procedures but that he believes the challenge to the ban would not stand.
"There are exemptions [to the law]," he said. "If there weren't, you could Botox your child, you could tattoo your child, you could circumcise your daughter. We have a legal team to defend the ban. We will defend it vigorously."
Jeremy Benjamin, a plaintiff in the case, called the measure anti-Semitic and said it singles his Jewish family out "as illegal and unwanted in our own city."
The Benjamins' son was circumcised "as Jews have done for thousands of years," he said. "This is our city, and we're standing up for ourselves and our family's freedom to live the life that we choose in this city."