Actually Registering doesn't permanently follow them. It just puts their information in the computers. You should know, it is nearly impossible to catch a very good spy. Also, it doesn't give a picture of the person, just the armor they use.
Eclipse doesn't have the tech, but they have other kinds that allow them to see through the armor of Eclipse memebers. It also lets them punish their members, or even kill them, if they blab secrets.
To register, a New Goverment agent, allows the nano bots of their suit to get information from the opponents armor.