Anarchy doesn't have to be permanent. Anarchy can exist to change the current system, an then evolve into something else. I approve of anarchy an overthrowing the current order because it's a corrupt mess. But certain rules need to exist, so to me anarchy is what would take place to overthrow the current order. An once that was acheived, autonomy should be next on the agenda.
1.) If there was no law or justice system then gangs would roam freely and who would stop anyone who refused to take part in a peaceful anarchy
As I've said, anarchy can just be a starting point. Most people who approve of anarchy see it as a starting point to getting something acheived, it's not something permanent. Once the old system is destroyed, it's time to make a new system, not remain in a state of permanent anarchy.
2.) How would people buy, sell, and gain jobs. How could the economy run if no jobs are put in place.
Who would want a system that doesn't work? For outright anarchy you need a lot of people commited to the cause, an most people don't want their world in shambles. People who work in government are not highly intelligent human beings who are the only people on Earth who know how to create a system that works. Their system doesn't work proficiently anyway. Humans are capable of governing themselves, because they usually want to make their living as comfortable as possible. As I've said, anarchy should be used as a starting point. Once the old system is gone, their is no need for anarchy. A new, better, fairer system can be created, based on what most people want. Not what a small group of corrupt upper class cretins want.