The legal observers have traveled from as far away as California, the Pittsburgh Post-Gazette reported. Many are local, law students from the University of Pittsburgh.
Their job is to monitor the interactions between police and protesters. Erin Gill, coordinating legal observers for the ACLU, called them the group's "eyes and ears."
The lawyers plan to be conspicuous, with those from the ACLU equipped with orange hats while the NLG is using bright green. They hope a visible presence will prevent police overreaction.
The observers, hats on, were already at work Tuesday in Point State Park where Seeds of Peace and other anti-war groups held a demonstration. They were also present later that night when police surrounded a Seeds of Peace bus.
At training sessions, lawyers are told to stay out of trouble.
"You're no good to us if you're arrested," Heidi Boghosian, NLG executive director, told one group.
2014: The Year in Music [PHOTOS]