How the unlawful arrest happened

3pm,Chief of security department of Shibuya police said to us "If you wt want to go the Prime minister's house by walk,that7s fine" and"you can go and see the house in group of 5to6 people each in turn" when we were gatheing in front of Shibuya train station.We did some anouncement of the tour for 30or40minutes,then about 50 of us started to walk.We held our signs and baloons,and we never used our speaker just as police told us to do.
Only 5 minutes later,when we were reaching Dogen Zaka Street one of our comrades who were holding a sign to show the way to other participant was held his arm and wrestled to the ground by police.Police officers stared to get a full nelson on other 2 participant with the cue saying"go!go!It's KOBO(Short term for "interfering with policemen in the execution of their duties")It's KOBO!" and then took away the 3. On the news report they say police gave us warning many times but there weren't any except when we started walking.The reason for the arrest of the 3 given by police are "breaching public safety ordinance" and "interfering with policemen in the execution of their duties"but it's all clear in recorded film that there were no such act.There are no fact that tour participants conducted violence.