Lots of discussions surround this term. So heres my take on it if I am wrong no doubt one of the guys will give there opinion or a better take on the subject. 99% of bikers are law abiding 1% choose to live by their laws. Or 99% of bikers wish to be like the 1% who live the life.
Most if not all 1%ers belong to "outlaw" mototcycle clubs. Outsiders are tolerated to a certain degree. If they are your friend keep them that way. They owe no loyalty to any body outside the club. Close friends can even be pushed aside or worse for fellow club members.
Be careful around them what we may take as fun or banter can easily be taken as an insult by them. They will never talk about club business with outsiders. If you do get into a situation with them know that they will rat pack you you will not fight one of them you will fight all of them.
Scotland is one of the few countries in the world ha does not have a Hells angels, Bandidos, Satans slaves chapter we do have the Blue Angels which are the longest established MC club in europe. The history section on the link below is quite interesting if you are interested in bikers clubs.
http://www.blueangelsscotland.com/base.html