Volunteer Protection Act
The Volunteer Protection Act of 1997 provides personal immunity to individuals who act on behalf of an organization in a volunteer capacity. Naturally the Act won’t protect a volunteer who willfully causes harm or engages in gross negligence. Equally, the Act may not absolve the organization from liability for its volunteers or keep the volunteers from being named as defendants in a lawsuit.
In addition, all states have some form of volunteer protection law with which the board should be familiar to determine its limitations and requirements e.g. specific language in the articles of incorporation and the bylaws.
Here is the text for the Volunteer Protection Act: http://www.t-tlaw.com/lr-15.htm