Mark, you are correct I posted the previous year, sorry.
http://www.modelaircraft.org/files/2013-2014CLAerobatics.pdfI did look up the current year and found this quote.
3.2
All aircraft that use electric propulsion shall have a positive arming device that, that when disarmed, mechanically prevents battery power from being applied to the motor.
This may be (but is not limited to) a switch, the existing battery plug, or arming plug, but must be in series with the main power line(s) from the battery and mechanically disconnect the battery from the motor. Relying on the timer, timer start switch, flight programmer, or any other low-level logic signal for this function is specifically excluded. The model shall be restrained at all times while the system is armed, either by the pilot (including holding the handle before, during, or after an official flight), an assistant, or mechanical restraint device (e.g. stooge). The device must be disarmed after flight before the airplane is left unrestrained. Failing to restrain the model while still armed during an official flight attempt shall result in official flight with a score of 0. The system may be armed in the pits as long as it is restrained at all times.
I don't see where arming plugs are mandatory, what I see is that you must be able to disconnect the power to the motor.
Not trying to ruffle any feathers. I would like to know what the requirements are so if I attend a competition in the US will my airplane comply!