What is De Facto?

Legal Definition
De facto (/d ˈfækt/, /d-/, Latin: [deː ˈfaktoː]) is a Latin expression that means "in fact, in reality, in actual existence, force, or possession, as a matter of fact" (literally "of fact"). In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially designated or established". It is commonly used in contrast to de jure (which means "according to law"; literally "from law"), when referring to matters of law, governance, or technique (such as standards) that are found in the common experience as created or developed without or contrary to a regulation. When discussing a legal situation, de jure designates what the law says, while de facto designates what happens in practice.
-- Wikipedia
Legal Definition
An action taken without strict legal authority to do so, but recognized as legally valid nonetheless.

See De Facto Corporation
Legal Definition
I. e. in deed. A term used to denote a thing actually done; a president of the United States de facto is one in the exercise of the executive power, and is distinguished from one, who being legally entitled to such power is ejected from it; the latter would be a president de jure. An officer de facto is frequently considered as an officer de jure, and his official acts are of equal validity. 10 S. & R. 250; 4 Binn. R. 371; 11 S. & R. 411, 414; Coxe, 318; 9 Mass. 231; 10 Mass. 290; 15 Mass. 180; 5 Pick. 487.
-- Bouviers Law Dictionary
Legal Definition
In fact, in deed, actually. This phrase is used to characterize an officer, a government, a past action or a state of affairs which exists actually and must be accepted for all practical purposes, but which is illegal or illegitimate. In this sense it is the contrary of de jure, which means rightful, legitimate, just or constitutional. Thus, an officer, king or government de facto ls one who is in actual possession of the office or supreme power, but by usurpation or without respect to lawful title; while an officer, king or governor de jure is one who has just claim and rightful title to the office or power, but who has never had plenary possession of the same or is not now in actual possession. 4 Bl. Comm. 77, 78.

So a wife de facto is one whose marriage is voidable by decree, as distinguished from a wife de jure or lawfui wife, 4 Kent, Comm. S6.

But the term is also frequently used independently of any distinction from de jure; thus a blockade de facto is a blockade which is actually maintained, as distinguished from a mere paper blockade. As to de facto "Corporation," "Court," "Domicile," "Covemment," and "Officer," see those titles.

In old English law. De facto means respecting or concerning the principal act of a murder, which was technically denominated factum. See Fleta, lib. 1, c. 27, § 18. See De facto contract.
-- Black's Law Dictionary
Legal Definition
As of fact; actually. See 8 Kan. 437.
-- Ballentine's Law Dictionary