kill switch

A kill switch is a safety mechanism used to immediately shut down machinery, a vehicle, a software program, or an electronic system when normal shutdown procedures are not fast or safe enough. 

Usually seen in automotive or marine vessels, the so-called kill switch describing the manner in which the U.S. President could turn off the internet refers primarily to taking action without a court having to approve the decision. It does not mean one person can turn off the net. Rather, various remote device wiping features on smartphones or enterprise tools, such as automated network isolation for rogue AI agents, would cut off unauthorized access from misbehaving code.