In law, a legal opinion is usually a written explanation by a judge or group of judges that accompanies an order or ruling in a case. Legal opinions may also be written by legal experts. A legal opinion is used to lay out the rationale (reasons for) and legal principles for the ruling.
|Judicial opinions & aggregates for official decisions (O.S-Federal)|
Opinions are usually published at the direction of the court. They may be used to reinforce, explain, change, establish, or overturn legal precedent. If a court decides that an opinion should be published, the opinion is included in a volume from a series of books called law reports or case reports. Published opinions of courts are also collectively referred to as case law, which is one of the major sources of law in common law legal systems.