Frivolous or vexatious
In the law of several jurisdictions, such as Ireland and New Zealand, frivolous or vexatious, when used to describe an action such as a complaint or a legal proceeding, is a term used to deny (or attempt to deny) its being heard, or to dismiss or strike out any ensuing judicial or non-judicial processes.
The term is not defined in statute law, but has been defined in legal cases. One of the earliest cases was Keaveney v. Geraghty, where the plaintiff's libel proceedings were stayed on the grounds that they were frivolous, vexatious, and an abuse of the process of the court. The plaintiff was effectively declared a vexatious litigant.
A case is frivolous if it has no reasonable chance of succeeding, and is vexatious if it would bring hardship on the opposite party to defend something which cannot succeed.
The term is used in many Acts of the Oireachtas and statutory instruments. For example, the Data Protection Commissioner shall investigate any complaint made to him about the contravention of the Data Protection Acts, unless he is of the opinion that it is frivolous or vexatious  and the head of a government department may refuse access to records under the Freedom of Information Act if the request is frivolous or vexatious. The High Court and Supreme Court may order an action to be stayed or dismissed, or judgment to be entered, where an action or defence is frivolous or vexatious.
-  I.R. 551
- Justice Barron, Farley vs Ireland & Others,  IESC 60 at page 1521
- Section 10 (b) (i) of the Data Protection Act, 1988
- Section 10 (1) (e) of the Freedom of Information Act, 1997
- Order 19, Rule 28 of the Rules of the Superior Courts
- "Isaac Wunder" orders, which may be made in the event of frivolous or vexatious litigation