Black markets, by definition, are not supported by the rule of law. There are no rights to own and dispose of property protected by the enforcement power of the state. There are no laws of contract or bankruptcy, or judicial review and determination again enforced by the state. The essential infrastructure of a market economy is missing.
Black markets offer few of the benefits of legally sanctioned trade. To know that the state will protect one’s rights to property will encourage the taking of risks that create wealth and foster growth. Few will risk their capital, however, if there is little assurance that the rewards of risk are secure from the arbitrary actions of government, or street mobs.