I'm not guessing. It depends on the state but generally religious organizations are exempt.
There is also this for Missouri:
Missouri Revised Statutes
Chapter 209
Aid to the Blind--Rights of Persons with Visual, Hearing or Physical
Section 209.321
August 28, 2010
4. A person is not considered to be interpreting pursuant to the provisions of this section if, in a casual setting and as defined by rule, a person is acting as an interpreter gratuitously or is engaged in interpreting incidental to traveling.
The above could be a way for a student interpreter to work without charging a fee.
Also, since AA meetings are confidential, who would blab to anyone "official" that so-and-so is interpreting the meetings if the student does share that information with anyone? That would be breaking the confidentiality of the meeting.
I was wondering the same thing when I thought it was a law. Thanks for the good news!