In English law and its derivatives, namely Australian, New Zealand, Canadian, South African, Indian, and U.S. legal doctrines, ex parte means a legal proceeding brought by one party in the absence of and without representation of or notification to the other party.
Where proceedings are heard ex parte, a high degree of candour is required, including full and fair disclosure of facts adverse to the moving party.
A failure to make such disclosure is ordinarily sufficient to warrant discharge of such order as might be made.
[3] The other use means 'on the application of' when used in the case name where prerogative relief is sought, such as a writ of prohibition, certiorari or mandamus.
[5] In the United States, the availability of ex parte orders or decrees from both federal and state courts is sharply limited by the Fifth and Fourteenth Amendments, which provide that a person shall not be deprived of any interest in liberty or property without due process of law.
For example, in the States of California and Illinois, ex parte proceedings are available if notice is given before 10 a.m. the previous court day, or even shorter upon showing of emergency need.
[13] In addition to the notice requirements, an ex parte application must contain an affirmative actual showing in a declaration based on personal knowledge of "irreparable harm, immediate danger, or any other statutory basis for granting relief ex parte".
The 'Regina' (or Rex if the monarch is a male) refers to the sovereign in whose name all judicial reviews are brought.