This implied duty requires that contracting parties do not act in a way that will destroy or injure the right of the other party to receive the benefits of the contract. Therefore, restrictions on alienation must be exercised in good faith and for a legitimate commercial purpose, not just for arbitrary or capricious reasons.
For example: If a lease contains a restriction on subletting, the lessor cannot arbitrarily deny permission simply because they dislike the sublessee; there must be a genuine business concern.