SAN FRANCISCO (CBS / AP) — The American Civil Liberties Union has filed a lawsuit challenging California’s new voter-approved law to boost penalties for those convicted of human trafficking.

Voters approved Proposition 35 on Tuesday with 81 percent of the vote, toughening the state’s penalties for human trafficking and its monitoring of sex offenders.

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In its lawsuit filed Wednesday in U.S. District Court in San Francisco, the ACLU of Northern California and the Electronic Frontier Foundation argue that another provision of the measure restricts the First Amendment rights of registered sex offenders.

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The initiative requires them to provide their Internet identifiers to authorities, which the groups say sets a dangerous precedent. They filed suit on behalf of registered sex offenders.

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