For instance – I worked in Belfast while a series of flag protests took place (https://en.m.wikipedia.org/wiki/Belfast_City_Hall_flag_prote...) in 2012. In my view, these protestors had every right to make their views publicly visible and known.
But when they organised "rings of steel" around the city, preventing drivers from coming and going about their business, as they did on a few occasions, they had gone too far.
I don't know the full details of the anti-monarchist arrests, but unless they were planning to disrupt the events, I feel they should not have been arrested.