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assert against
対抗
To be able to rely on a right, or on a fact about it, against someone who is not a party to it. Acquiring, losing or changing a right in rem (物権) in land or a building cannot be asserted against third parties until it is registered (登記) (Civil Code, Article 177), and a registered lease of land or a building can be asserted against a person who acquires a right in rem in it, such as a buyer, and against other third parties (Article 605). The Act on Land and Building Leases lets a tenant do without registering the lease itself: a right to use land for a building (借地権) can be asserted against third parties once the tenant owns a registered building on the land (Article 10, paragraph (1)), and a building lease takes effect against anyone who later acquires a right in rem in the building, such as a new owner, once the building has been handed over (Article 31). Some rules protect only a third party who did not know: a rescission for fraud cannot be asserted against a third party who did not know of the fraud and was not careless in not knowing (善意でかつ過失がない) (Civil Code, Article 96, paragraph (3)).
Written by AI using Civil Code, Arts. 96, 177, 605 and Act on Land and Building Leases, Arts. 10, 31 as a reference.