An actual court in the US will probably not try to legislate whether a person is of the Jewish faith or not, _regardless_ of what some other religious "court" says.

Probably (IANAL) if a person says that they observe the Jewish faith and that this is a deeply held belief, regardless of whether some religious organization recognizes him/her, that will be enough for the courts.

Sorry, I was talking from the believer's point of view; not from a law perspective. You are probably right about that.