Its is reported in the press that all marches had been banned until the end of the year. Here is a link,
https://en.m.wikipedia.org/wiki/Bloody_Sunday_(1972)
Some elements of an Irish mob in those days was likely to be armed, the IRA was active and at ‘war’ trying to kill soldiers. Ulster was a nasty place to be and those nationalist murderers seem to have got away with their murders.