go off the reservation

• go off the res
• go off the rez

By analogy with a member of the tribe leaving an Indian reservation.[1]

go off the reservation (third-person singular simple present goes off the reservation, present participle going off the reservation, simple past went off the reservation, past participle gone off the reservation)

1. (literally, derogatory) To leave an Indian reservation to which one was restricted.
   • 1872 April 10, United States Congress, The Congressional Globe, page 2332:

     The Indian may go off the reservation, he can steal from the whites and run back to the reservation with impunity.

2. (US, politics) To break with one's party or group, usually temporarily.
   • 1943, Paul De Kruif, Kaiser Wakes the Doctors‎, page 79:

     This hand was ready to give the works to any physician, a member of the Medical Association in good standing, who'd go off the reservation by daring to serve a medical co-operative on a full-time salary.

   • 1960 January 31, Harry S Truman, “Dear Joe”, in Monte M. Poen, editor, Strictly Personal and Confidential: The Letters Harry Truman Never Mailed‎, published 1999, →ISBN, page 137:

     I'll never forget 1948 when these so called "liberals" (synthetics I call them) went off the reservation and gave New York to Dewey.

3. (by extension) To engage in disruptive activity outside normal bounds.
   • 1965, Drew Middleton, The Atlantic Community: A Study in Unity and Disunity‎, page 186:

     When the Russians do go off the reservation, as they did early in April 1965, their object is not to challenge the Western allies of yesteryear, the United States, Britain, and France, but to impress upon West Germany their support for East Germany and its claim to West Berlin.

4. (by extension) To act in an independent, uncontrolled, or unauthorized manner.
   • 2021 November 14, HarryBlank, “Over/”, in SCP Foundation‎, archived from the original on 5 February 2023:

     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?"

• jump the reservation
• go beyond the pale
• go rogue

• off the reservation

• off reserve, off-reserve (Canada)