Venture "City" is a city in name only -- defined by the companies that declare themselves as within the city, and the recognition from other companies. This makes the border of the city fluctuate by what companies are recognized, though AEGIS Security declares all those company properties that pay for security services are within the City.
There is no city government, exactly, rather layers of potentially overlapping corporate policy. Policies in a corporate zone are enforced through private security, such as AEGIS Security, and possibly private meta-human contracts through the Meta Net. The only other things really legally enforceable contracts.
For companies, contracts are laws, made to be creatively broken. Being in a corporate zone technically means accepting their implied contract. ("By being here, you agree to the following:") Contracts can be between people (though sprawls have a harder time entering contracts) For contracts, there is also a form of peer pressure amongst corporations and a reputation for not honoring contracts you signed is bad for business, and there are companies that are paid to be honest and fair (or as fair as they can be, depending on who is paying them)
Arbiters help with the creation and interpretation of contracts