SANTA MONICA, Calif. — When a group of activists proposed banning circumcision in San Francisco last fall, many people simply brushed them aside. Even in that liberal seaside city, it seemed implausible that thousands of people would support an effort to outlaw an ancient ritual that Jews and Muslims believe fulfills a commandment issued by God.

But last month, the group collected the more than 7,100 signatures needed to get a measure on the fall ballot that would make it illegal to snip the foreskin of a minor within city limits. Now a similar effort is under way in Santa Monica to get such a measure on the ballot for November 2012.

If the anticircumcision activists (they prefer the term “intactivists”) have their way, cities across the country may be voting on whether to criminalize a practice that is common in many American hospitals. Activists say the measures would protect children from an unnecessary medical procedure, calling it “male genital mutilation.”

“This is the furthest we’ve gotten, and it is a huge step for us,” said Matthew Hess, an activist based in San Diego who wrote both bills.