Smart contracts are not going to instantly replace government with a techno-libertarian utopia. They are going to make government, lawyer and bank services a lot less necessary. And, they are going to provide a lot of alternative services to people without access to effective government/financial services.
Smart contracts can’t observe anything but time, crypto and signaling from users/automated services. For disputes you need an independent third party to cast a deciding vote. A government judge is common option. But, you and I can agree to grant that vote to a non-government agent instead.
Legal rental contracts are non-trivial. A rental smart contract would similarly require more rules than we care to spell out here. But, “If the tenant and the notary both vote that there is bullshittery going on with the property, rent is suspended.” sounds like a reasonable thing to include.