I can't speak to general rules because I have only had experience with a few protest areas, never directly the black block, but can speak about my experience.

I mentioned about a protest at Queens Park up the tread.  At that particular protest, as I mentioned there was no violence per say but the protestor did act in a way that compelled the police to act.

In that situation I, personally, see what the protestor did as sympolic.  It was a way of bringing out for all to see exactly what we do.  He tried to equalize the Haudensaunee, his nation, and Canada, our nation by raising both flags together.  Canada would not exist except for the ability for them to accept us and treat us as equals and it was only in this  act of treating us as equals that allowed us to get to the point where we made their governments illegal and made their people not people.

So what did we do?  The agents of the government, who have been assured by the government that they are acting rightly and justly through years of teaching what they deem to be appropriate history, did not allow him to carry out this symbolic act but instead came in and forcibly arrested him just as they had all those before him.  Anyone witnessing that event or even hearing about the event can not deny what the governments attitude toward the Haudensaunee in particular and FN people in general are.

I see the protests in Brantford, Cayuga and Haggersville the same only less symbolic and more reality.

On a day to day basis the Haudensaunee land is being taken.  The government keeps saying we will talk later and in the words of Smitheman "they won't get it back".  They go to the construction sites and stop construction.  Some consider this economic assult and indeed the protests have escalated as well to include violence.  Why is that?  One reason is because the police initially stopped the workers from working and kept the construction crew and builders off site because of the Ipperwash Inquiry, however recently this has not been happening.  We have decided that our want to keep our colonialist version of captalism going is more important than their right to their treaty land or say over their treaty land.  Our wants are more important their their rights.  When violence happens it is because they are standing up for their rights because no one else will.  They are not willing to back down.  If they have to meet a violent confrontation they will but of the people that I have talked with who were involved in the more violent confrontations they didn't initiate anything.  They stood their ground and if it staying non violent meant that they would have to back down they refused to do that, they were willing to meet whatever came their way to stand up for themselves, again because no one else will.

One memory I have is from the highway bypass blockade last April.  At one point the police said they were going to come in and clear everyone out.  I was standing on the bridge above the blockade with about 200 people.  Below me there were about 20 Warriors on the road and double that on the hill.  They were waiting.  Their actions at this point had been non violent.  But they were willing to meet what came to them.