I don't think I can vote on this because both systems could be used, a justice system and a player system and also an automatic system.
I think i'll have to study or think about this more but my opinion has always been to keep the original guard zones around cities but to expand on them and to have much greater detail in the way of resources and reasons to leave the safe zones.
The system where you cut the head off of a person, was a good system because players could target crime and had an incentive. This system could be reworked so that it could not be abused by removing any repeating.
So, some type of code would be written that would bank 25 names then when a new name came into the bank it would be accepted as one and push the first name out of the bank. So, you could basically set this as a profession, Bounty Hunter because the person doing this would have to work hard to be able to gain one reward.
So, rather than setting a set number on the PK, make it so the bounty hunter has to collect so many bounties. So, if it would turn out that the bounty hunter had 25 friends who were red, they could each have a bank of 25 names also. So, each PK would need to be killed by 25 different people and each bounty hunter would have to bounty 25 different pks to have 1 bounty count. It's alittle mind boggeling, actually but i'm sure that a definite balance could be attained.
Another example might be to reward the bounty hunter with an item that they can only use.
The Justice System is very important because it will dictate how a player should think and it will set their demeanor. It's kind of like saying to the player, These are the rules we've set. If you abuse them, we have these penalties but it also says, Take it a step further and your account may be banned.
So, The Justice System not only protects people within a guard zone, it also shows, Look, the guard is stopping someone from murdering someone. The guard is stopping someone from stealing. The guard does not like the words that you are using.
This type of system also allows for freedom outside of the guard zone but you would still need an automatic system that also has rules, that say, If you kill someone, no matter where it is, it goes on your record and if you kill many people you get marked as a murderer and lose privileges.
So, all 3 of these systems could be designed to work in harmony. A type of militia or army or maybe even sign up and be a guard or seperate from that, bounty hunter system.
A Justice System could also involve very important things, such as a trial. That would be a great event. Jail time, fines, the guilatine, the stocks, dunking. Some things could be automatically set. You know what happens if you kill someone and get caught. You know what happens if you kill a few people and steal from them but maybe there will be situations where people are decided to be a griefer and they must appear in court, infront of their peers.
If they do not appear, then their account will be banned. I know, i'm just rambling but the idea is, is that these systems could work and they could work very well.