Employers in California and Illinois will no longer be able to force their workers to provide their Facebook passwords.
The new law is one of 400 state measures created in 2012 that are expected to take effect in 2013.
The social media policy will prohibit bosses from asking for password to personal employee accounts as well as the accounts of job applicants.
However, experts recommend that job applicants are still cautious about their social media activity since employers can still view information that is publicly available.
Michigan passed a similar measure in which educational institutions can be punished for not admitting a student because they did not provide passwords to their personal accounts such as their email or social media pages.
Among the other 2013 policies, teachers in Oregon will be allowed to report suspicious, bullying behaviors that they find on social media sites to proper authorities.
According to the National Conference of State Legislatures, some of the measures taking effect include issues such as consumer protection, gun control, health care, abortion, pension reform and same-sex marriage. While some of the laws took effect at midnight, others will take effect later in the year.