What rights or authority does an ex officio member of a governmental body have?

Blacks Law Dictionary (5th ed.) defines ex officio as "[f]rom office; by virtue of the office; without any other warrant or appointment than that resulting from the holding of a particular office." This means a true ex officio member of a governmental body holds his or her membership by virtue of holding some other office. Accordingly, there is generally no distinction between the rights and powers of an ex officio member of a committee and a "regular" member of the committee. See Robert’s Rules of Order Newly Revised (10th ed.) pp. 466 & 480. The distinction between the two is their path to membership not their authority.

For example, a municipal ordinance may designate the mayor as a member of a particular committee. Therefore, the mayor is an ex officio member of the committee because he/she is the mayor. As such, he/she holds all the rights and powers of every other member of the committee including the right to vote, etc.

The phrase ex officio is commonly misunderstood to mean non-voting. This is incorrect. Accordingly, unless this understanding (non-voting) is expressly stated in an ordinance, it may  not be to establish it by legal interpretation in light of the general rule regarding the rights and powers attached to ex officio membership. Therefore, an ordinance that is intended to make this designation (non-voting) but does not expressly limit the rights and powers attached to ex officio membership would be substantially improved by eliminating any reference to ex officio status and simply indicating that the designated official is a non-voting member of the particular governmental body.