I agree with john bunyan. This case is a typical "test" of the law.
The Health & Safety legislation has caused more problems than enough with people being restricted in doing their jobs in a sensible manner. Not so long ago it was emergency crews being unable to rescue an individual from water as they didn`t have the correct life vests. When will such silliness stop. Perhaps when firemen are prevented from approaching fires because they may be burned or paramedics/nurses/doctors from treating people because they may catch something.
I did my police riot traing at Royal Marine Commando Barracks at Eastney with Marines playing the rioters. They were set up to throw everything at us including molotov cocktails. Only rule was they had to throw them at the ground in front of us. Don't see H&S allowing that nowadays