A couple of thoughts. (First of all I go to AA not NA but I consider this a minor difference).
Court ordered AA has been ruled illegal in many places because of the religous aspect of the program. I can only assume NA would fall in the same boat.
Secondly, many of the AA groups in my area refuse to sign court slips. There were 1 or 2 judges that were momentarily pissed off, but they are powerless here as no one in any particular AA group has been court ordered to do anything. Your local NA groups might consider this in their next group conscience meeting.