How are fines from a homeowner's association legal?

I am trying to figure out what law grants home owners associations the authority to legally fine a homeowner? From my readings, I can't find a single state that allows penalty clauses in civil law but I see no disputes on homeowner’s association or condo association fines. Am I missing something? From my readings in civil law, the only remedy close to a fine is liquidated damages. They are legal because they are a pre-agreed way to compensate purchaser, who has suffered loss as a result of actions (or inactions) by the other. A penalty is intended as a punishment for some sort of failure and bears no relation to the actual quantum of loss suffered. A fine like this is unenforceable as only the government is granted that type of authority. Since violating a homeowner’s association bylaws like watering the lawn on Sunday or allowing a repair man after hours is causing no harm or loss, where do they get the authority to impose a fine? I ask because when my attorney writes me a standard wholesaler contract, I am always told that penalties are unenforceable and can only use an LD that assesses my losses. Am I missing something that a HOA is allowed to do something that an ordinary citizen cannot? Has this just never be challenged and people just pay the fine?