On the surface, voluntary codes of ethics are a good thing. They signal to a constituency that a particular group of individuals will hold themselves to a higher standard. The reality is, they're meaningless if there is no enforcement mechanism.
As far as the Loudoun board of Supervisors deciding not to have a code of ethics during this term, my thoughts are this: while implementing a code of ethics is a good PR move, if it's not going to be enforced, and the politicians are planning on acting unscrupulously whether or not there is one in place, it really doesn't matter if they have one or not.
The fact of the matter is this, several fields do not employ codes of ethics, including my own; Economics. Generally speaking, the only true value of a code of ethics is simply the piece of paper it's written on, especially if it's unenforceable, as they have been historically with the Loudoun Board of Supervisors.