"The arm's length principle (ALP) depicts the condition or the fact that the parties involved in a transaction are on equal footing and independent; these transactions are called "arm's-length transactions". This principle is used especially in the field of contract law in order to arrange an agreement that is legally acceptable, even if the parties are seen to be too closely related to be completely independent (e.g., when there are familial ties between the parties) or when the parties have shared interests (e.g., employer-employee)."

This is the formulation I seem to come up against in quite a lot of Czech contracts

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