go off the reservation

verb4

1. •
   (offensive) To leave an Indian reservation to which one was restricted.

   • The Indian may go off the reservation, he can steal from the whites and run back to the reservation with impunity. — 1872
2. •
   (US) To break with one's party or group, usually temporarily.

   • I'll never forget 1948 when these so called "liberals" (synthetics I call them) went off the reservation and gave New York to Dewey. — 1960
3. •
   To engage in disruptive activity outside normal bounds.
4. •
   To act in an independent, uncontrolled, or unauthorized manner.

   • The technician mentally recalibrated. "Yes ma'am. An Alpha-9-associated device just went offline unexpectedly." She raised an eyebrow. "Thompson and Adams gone off the res again?" — 2021