Proposition 35, known as the Californians Against Sexual Exploitation Act, outlined plans to make sex trafficking of a minor with force or fraud punishable with up to life imprisonment, increase fines for the offence from $100,000 (£62,500) to as much as $1.5 million (£937,500), and expand the crime to include the creation and distribution of child pornography.
It was one of the many issues listed on Tuesday's presidential election ballot as Californians headed to the polls, and the bill was passed by an overwhelming majority of 81.1 per cent.
An ecstatic Pinkett Smith, a longtime activist against human trafficking, took to her Don't Sell Bodies campaign website to mark the act's success in a blog post titled, "Prop 35 passed! Freedom shall reign!".
The Matrix Reloaded star writes, "California has sent a strong message that we will not tolerate human trafficking in the state of California.
"Our new initiative suggests that trafficking in California is unacceptable and a huge risk for criminals to participate in. We still must remember that there is much effort needed towards building programs in our communities and in law enforcement that focus on the safety and rehabilitation of survivors.
"Passing this new law is only the beginning, but today lets celebrate this beautiful beginning. Congrats California."