It could be considered arbitration of making yourself subject to it was voluntary. It's not.
If you are a Muslim, rejecting Sharia in favor of US courts makes you an apostate. Being an apostate carries the death penalty under Islam. If a Sharia court is available, Muslims MUST accept its jurisdiction and abide by its judgement, or be declared apostate.
I think this thread just wound its’ way through to the correct answer.
Allowing this court effectively enlists muslims into a choice of being compliant or being an apostate - and suffer brutal consequences handed down by such a sharia court. There should be NO tolerance on this. You want a sharia compliant society then GTFO.