Rothbard, from his 1991 Rothbard-Rockwell Report article, "The 'New Fusionism': A Movement For Our Time":
In a country, or a world, of totally private property, including streets, and private contractual neighborhoods consisting of property-owners, these owners can make any sort of neighborhood-contracts they wish. In practice, then, the country would be a truly "gorgeous mosaic," ... ranging from rowdy Greenwich Village-type contractual neighborhoods, to socially conservative homogeneous WASP neighborhoods. Remember that all deeds and covenants would once again be totally legal and enforceable, with no meddling government restrictions upon them. So that considering the drug question, if a proprietary neighborhood contracted that no one would use drugs, and Jones violated the contract and used them, he fellow community-contractors could simply enforce the contract and kick him out. Or, since no advance contract can allow for all conceivable circumstances, suppose that Smith became so personally obnoxious that his fellow neighborhood-owners wanted him ejected. They would then have to buy him out—probably on terms set contractually in advance in accordance with some "obnoxious" clause.
Elsewhere (in Nations By Consent: Decomposing the Nation-State, which you favorably cite elsewhere in Democracy), Rothbard similarly writes:
With every locale and neighborhood owned by private firms, corporations, or contractual communities, true diversity would reign, in accordance with the preferences of each community. Some neighborhoods would be ethnically or economically diverse, while others would be ethnically or economically homogeneous. Some localities would permit pornography or prostitution or drugs or abortion, others would prohibit any or all of them. The prohibitions would not be state imposed, but would simply be requirements for residence or use of some person's or community's land area.