Reading an old post.
Not sure if it varies from state to state.
Some jurisdictions require organizations (congregations, etc.) to have by-laws that readily available, and also to maintain an up-to-date membership list, readily viewable by any member. (Readily - not kept at the Secretary's house, but available at the hall after the meeting.)
The old post ( http://www.jehovahs-witness.com/topic/231734/congregation-laws ) indicates that the the boilerplate by-laws provided by HQ includes;
"Anyone meeting these requirements who is at least 18 years of age shall be designated a member of the Congregation."
If required by your state, they are registered with the state and available (usually for a modest fee).
Has anyone pulled the by-laws in their congo?
A few questions for the 18+ states.
If a resolution is voted on, with under-18's voting, should that resolution not be invalid?
If an under-18 cannot become a member, how can he/she be removed as a member (DF'd)?