said by Mike_27 :

Here's a public standard:
WISPA CALEA Standards (Versions 1 and 2) as produced by the WISPA CALEA Committee and ratified in May 2008.
»www.wispa.org/calea/WCS/

There are also cost effective solutions for small providers:
Netequalizer: »www.netequalizer.com/caleafaq.php
Mikrotik: »wiki.mikrotik.com/wiki/Calea

HTH,
Mike

said by bzmeteorite :

CALEA seems to be poorly designed in some respects, for one, there is no publicly published open standard out there that I am aware of, and two, the cost burden is completely on ISPs. That may not matter for the large ISPs, but for the smaller ones I'm sure it does.