I've no idea actually, I assumed they did, Democracy and all that. I think it is wrong, unless the gang is obviously a criminal one. Maybe the Hell's Angel should be allowed to wear their colours in Thailand, as anyone else should. What would the Angels say if I wore their colours? lol, I doubt they would say anyone has the right to wear what they want!
I met a bunch of Confederates bikies at a Port Ferry festival once, decent blokes. My brother-in-law owned a nightclub in Melbourne with a senior bikie, my sister helped a patient recover from a gunshot - he was the head of a bikie gang and she said he was very nice, mind you so was Tony Soprano lol.
I shared a flat in Scotland with a 1%er, who was a really nice guy, It was only after he moved out that I found out if he had been arrested for dealing Class A drugs(on a large scale), I'm the one who would have gone down, being my flat and all. A great guy, always very generous with his dope, and never in any scraps when we went out. However, his mates were hardcore and I had been in a fight with one previously when I was a punk. Most the ones I met and who came to my flat had all done time in prison. The one who lived there was given 3 years in Perth jail 9 months later, could easily have been me, but again a really nice guy.
So, you are right, they shouldn't be able to ban all colours in Oz, but I don't think foreigners here should be able to show the colours of famous outlaw gangs, after having insight into some of these gangs. Most Thais don't realize the truth about them.