For example, an appellate brief to the highest court in a jurisdiction calls for a formal style—this shows proper respect for the court and for the legal matter at issue.
An interoffice legal memorandum to a supervisor can probably be less formal—though not colloquial—because it is an in-house decision-making tool, not a court document.
In the United States, in most law schools students must learn legal writing; the courses focus on: (1) predictive analysis, i.e., an outcome-predicting memorandum (positive or negative) of a given action for the attorney's client; and (2) persuasive analysis, e.g., motions and briefs.
Many lawyers use and re-use written documents in this way and call these re-usable documents templates or, less commonly, forms.Persuasive writing is the most rhetorically stylized.So although a brief states the legal issues, describes authorities, and applies authorities to the question—as does a memorandum—the brief's application portion is framed as an argument.Legal writing is a type of technical writing used by lawyers, judges, legislators, and others in law to express legal analysis and legal rights and duties.Legal writing in practice is used to advocate for or to express the resolution of a client's legal matter. In most legal writing, the writer must back up assertions and statements with citations to authority.