Prohibiting Detention of Youth Status Offenders Act of 2017 This bill amends the Juvenile Justice and Delinquency Prevention Act of 1974 to modify the deinstitutionalization of status offenders (DSO) core requirement with which a state must comply to receive funds under the Formula Grant Program. The DSO core requirement prohibits the secure detention or confinement of a juvenile who commits a status offense (i.e., an offense that would not be a crime if committed by an adult). This bill eliminates an exception to the DSO core requirement that permits the secure detention or confinement of an out-of-state runaway youth. It also eliminates, not later than one year after enactment, an exception to the DSO core requirement that permits the secure detention or confinement of a juvenile status offender who violates a valid court order. Until then, use of the valid court order exception to securely detain or confine a juvenile status offender must comply with additional requirements, such as issuance of a written court order and a three-day maximum length of detention.