Otago University Norml spokesman Abe Gray said the university installed the cameras about three weeks ago as part of the recently completed refurbishment of the union building.
The group was particularly concerned about a camera attached to the outside of the union building, which had a "360-degree view" of the area where people met for "4:20" protests, Mr Gray said.
The group was worried the university was using the cameras to "keep tabs" on who participated in the protest and scare people away from joining in.
The bi-weekly meetings were a legitimate form of protest aimed at cannabis law reform, he said.
Otago University director of student services David Richardson said the cameras were there to ensure the campus was safe and that they were installed whenever the university carried out new developments.
"The CCTV system for the union redevelopment is no different. The cameras were placed in areas that would obtain the best coverage," Mr Richardson said.
