California Code, Penal Code - PEN § 3454

(a) Each supervising county agency, as established by the county board of supervisors pursuant to subdivision (a) of Section 3451, shall establish a review process for assessing and refining a person's program of postrelease supervision. Any additional postrelease supervision conditions shall be reasonably related to the underlying offense for which the offender spent time in prison, or to the offender's risk of recidivism, and the offender's criminal history, and be otherwise consistent with law.

(b) Each county agency responsible for postrelease supervision, as established by the county board of supervisors pursuant to subdivision (a) of Section 3451, may determine additional appropriate conditions of supervision listed in Section 3453 consistent with public safety, including the use of continuous electronic monitoring as defined in Section 1210.7, order the provision of appropriate rehabilitation and treatment services, determine appropriate incentives, and determine and order appropriate responses to alleged violations, which can include, but shall not be limited to, immediate, structured, and intermediate sanctions up to and including referral to a reentry court pursuant to Section 3015, or flash incarceration in a city or county jail. Periods of flash incarceration are encouraged as one method of punishment for violations of an offender's condition of postrelease supervision.

(c) As used in this title, “flash incarceration” is a period of detention in a city or county jail due to a violation of an offender's conditions of postrelease supervision. The length of the detention period can range between one and 10 consecutive days. Flash incarceration is a tool that may be used by each county agency responsible for postrelease supervision. Shorter, but if necessary more frequent, periods of detention for violations of an offender's postrelease supervision conditions shall appropriately punish an offender while preventing the disruption in a work or home establishment that typically arises from longer term revocations.