It was formerly the practice in English courts, for example, to treat as impermissible in a lawyer's argument or a judge's opinion a reference to a secondary source written by a still-living author. If the author of a treatise or (rarely) an article was dead, then citation was permissible, but not otherwise. The reasons for this practice remain somewhat obscure, although apparently it developed out of a concern that it was far easier for those who are still living than those who are dead to change their minds. What is important, however, is that the prohibition gradually withered, a withering that commenced more or less with the citation by the House of Lords in 1945 to a work by the then still-living Arthur Goodhart. Once the first citation to a living secondary author appeared, subsequent courts became slightly less hesitant to do the same thing, and then less hesitant yet, and over time the practice became more widely acceptable.

Unknown, Frederick Schauer - Thinkin…, loc. 147