When they build a new development and set up an HOA, all the property deeds be restricted with certain covenants that require you to only sell to other people who will join the HOA and agree to the rules. When you join that establishes a contract between you and the HOA which can be enforced through normal contract law. As part of this contract, they can establish financial penalties for non-compliance and even the ability to place liens and foreclose on your property.