The American Civil Liberties Union of Minnesota sued the city of St. Paul Tuesday.
The ACLU is asking a judge to re-instate the demonstration permits of two protest groups before next week's Republican National Convention.
St. Paul city attorney John Choi said the city had to revoke the permits for Hamm Plaza because its location posed a number of security and transportation concerns.
Choi said the city should have never issued the permit in the first place.
"I think ultimately what the situation was, was that a permit was issued for Hamm's Plaza, and the city not totally understanding where the park was. If you know anything about Hamm's Plaza, it's just a small little circular concrete area, kind of behind the Landmark Center and front of the Travelers Building. You'll see a lot of skateboarders use that area. It's not a very big piece of land, and I think there was some confusion about whether or not that park was located somewhere else," Choi said.
The Welfare Rights Committee and activist Ben Plunkett were notified in early August that the city was retracting their permits.
The city has offered them other locations.