A voluntary association of independent states is a confederacy.
commonwealth
confederation
Confederation referred to the group of colonies (which became states) banding together in order to more strongly represent their shared interests, especially with regard to dealing with the British.
independent states.
A loose association of independent states that agree to cooperate on specified matters.
The Commonwealth of Independent States is an association of sovereign nations and has no capitol of its own. Its largest city is Moscow, Russia, and its administrative headquarters are in Minsk, Belarus
In the United States, rating films is a voluntary system operated by The Motion Picture Association of America. Even though the system is voluntary, most theater chains will not show an unrated film.
A loose association of states is called a confederation. This system involves independent states coming together for common purposes while retaining their sovereignty and independence. Each member state in a confederation typically retains a significant degree of autonomy and authority.
The Association For Independent Music has a hall of fame, so this could be what you are looking for. The American Association of Independent Music, or A2IM, is a non-profit Trade Organization representing independent record labels in the United States. http://en.wikipedia.org/wiki/AFIM However, there is also the Association for Family Interactive Media. http://www.afim.org/
The World Religious Travel Association filed a voluntary petition for relief under Chapter 7 of the Bankruptcy Code in the United States Bankruptcy Court for the District of Colorado on Jan. 7, 2011.
CIS stands for Commonwealth of Independent States, which is an association of former Soviet republics. It is not a nationality, but rather a geopolitical organization. Members include countries such as Russia, Ukraine, Belarus, and Kazakhstan, among others.
States joined the Union on a voluntary basis.