You are right in respect to my commend regarding gathering evidence - it cannot be used as evidence in any U.S. court. I forgot about this difference between the U.S. law and the one in my country. However, as you have noted, it may be submitted in an effort to initiate an investigation, and probably that was the reason they gathered it in addition to publishing the footage of unlawful acts that were commited on this property (there is a ground-based video on YT of them shooting and stomping on pigeons).
To all guys and gals who raise the privacy question: the club and its patrons were actually those who violated the law, but the district attorney is reluctant to prosecute them. The activists were gathering evidence, legally or not.