From AMA document 5010-a, "SAFETY REGULATIONS FOR MODEL AIRCRAFT POWERED BY GAS TURBINES":

The fuel system shall have two fuel shut off provisions, one of which is manual and the other one must be remotely operated. An ECU operated shut down is compliant as a remote shut off if it closes with loss of power.

Thus, for most of us in the US with standard off-the-shelf engines, the ECU-controlled fuel solenoid is required.

Bob