[For more current case annotated texts by this author, see Bernstein & Lookofsky, Understanding the CISG in Europe, 2d ed. (2003) and Lookofsky, Understanding the CISG in the USA, 2d ed. (2004).]
321. If the buyer is in delay in taking delivery of the goods and, even though the risk of loss may have passed, the seller is either in possession of the goods or otherwise able to control their disposition, the seller must take such steps as are reasonable in the circumstances to preserve them; the same applies where payment of the price and delivery of the goods are to be made concurrently, and the buyer fails to pay the price.
In either case, in exchange for fulfilling his duty to preserve the goods, the seller in possession acquires a right of retention akin to a 'mechanic's lien,' in that he is entitled to retain the goods until he has been reimbursed for his reasonable expenses by the buyer.