A rule or principle of the law established through the repeated application of legal precedents. Common law lawyers use this term to refer to an established method of resolving similar fact or legal issues as in "the doctrine of stare decisis".
Jurists with a civil law leaning use this refer to the least authoritative of the three main sources of legal research. After (1) statutes or legislation, and (2) judgments, there are writings by learned authors, such as articles in law journals, hard-copy of electronic, or law books (such as The Law of Contracts by S. M. Waddams, Canada Law Book Inc., Toronto, 1999).
The Internet is breeding a fourth level, based on reliability, such as this website duhaime.org or Wikipedia, which publishes not to the profession per se, but to the common folk, much as Blackstone did; and now, even a fifth set: lawyer blogs, which may have interspersed within their texts, opinions on the law.
