But remember that facial recognition is far from the only way to identify protesters. Assume that the full power of the DHS is there (drones, Stingrays / IMSI catchers, license plate readers)
>>samsta+(OP)
Once a face is captured that image data can be retained forever while the image recognition continually improves and then repeatedly reprocessed for matches. Best not to show your face at all if you don't want to be held accountable.