The Democrat signed the measure Thursday.
The new law codifies certain policies already in place at the state Department of Corrections.
Under the measure, inmates are prohibited from being placed isolated confinement unless there is “reasonable cause” that the inmate or others would be a serious risk of harm.
The law also prohibits certain members of vulnerable populations from being isolated except in rare instances. Those populations include inmates under 21 and over 65, those with disabilities, pregnant women and LGBTQ individuals.
The law also bars inmates form being placed in isolated confinement for more than 20 consecutive days, or for more than 30 days during any 60-day period.