What it actually decides.
A ground fault circuit interrupter compares the current going out against the current coming back. A difference means some of it is returning by another route, which in practice means through a person or through water, and the device opens the circuit in a fraction of a second.
At temporary events the requirement is specific rather than general. The electrical code article covering carnivals, fairs and similar temporary installations requires ground fault protection on ordinary 15 and 20 amp, 125 volt non-locking receptacles that the public can readily reach, and on equipment supplied from them. The protection may be in the receptacle, in the plug, or in a cord set within a short distance of the plug.
There is an exclusion that looks wrong and is deliberate: egress lighting may not be on ground fault protection. The reasoning is that a nuisance trip which plunges an exit route into darkness is more dangerous than the fault the device is guarding against.
Two cautions belong with this. The article quoted above is written for outdoor and portable-structure events; an indoor performance area falls under a different article, and which one an inspector applies is their call. And the code edition in force varies by jurisdiction and is revised. For a show in South Florida the operative question is always which edition this county has adopted, not what the national document says this year.
We own this equipment.
Municipal event production — owned inventory, our own crew, and a site survey before anything is specified.