Catherine Allen, Aoiffe Moran and Lauren McCausland

The recent Supreme Court decision of M v M [2026] IESC 2 provides welcome clarity, and reaffirmation of the law concerning litigation restriction orders, also known as Isaac Wunder orders.

A court may make an Isaac Wunder order restraining a person from bringing any further proceedings without first obtaining the permission of the court where it is satisfied that a litigant has persistently brought vexatious or frivolous proceedings.

An Isaac Wunder order is not a new concept and derives its name from a Supreme Court decision in Wunder v Irish Hospitals Trust (1940) Ltd.

A subsequent 2001 decision of Riordan v An Taoiseach (No 4) [2001] IESC 83 affirmed the broad and inherent jurisdiction of the courts to make these orders where it is necessary to protect parties “from unnecessary harassment and expenses” and to prevent abuses of court processes.

Background to the case

The Supreme Court revisited the issue in January 2026 in the case of M v M. This case involved protracted family law proceedings concerning child access and maintenance.

Following a District Court order concerning access arrangements, an appeal was lodged to the Circuit Court.

The Circuit Court made a final determination on access and maintenance and granted an Isaac Wunder order to prevent them from issuing further proceedings against the respondent in the District Court, the Circuit Court or in any other court without first obtaining permission from the Circuit Court.

High Court

The appellant sought leave from the High Court to judicially review the Circuit Court decision. They argued that the Circuit Court had admitted into evidence material that was neither on affidavit nor given in oral testimony and had not permitted cross-examination of the respondent.

Leave was initially granted, however the respondent successfully applied to set aside this leave. They succeeded on the basis that the affidavit grounding the leave application was manifestly and factually incorrect and did not detail the history of the litigation before the Circuit Court.

The High Court however ruled that, although it can restrict litigants from bringing proceedings in the lower courts, the Circuit Court cannot block access to the High Court by requiring prior permission be obtained from the Circuit Court before judicial review proceedings are issued.

Court of Appeal

Having been unsuccessful in the High Court, the appellant appealed that decision to the Court of Appeal arguing that the finding of material non-disclosure was incorrect.

Both parties agreed that the Court of Appeal would quash and freshly consider whether to grant an Isaac Wunder order.

The Court of Appeal, in granting the Isaac Wunder order, had regard to the following factors, which were subsequently approved by the Supreme Court:

1. whether the appellant had brought one or more actions to determine an issue already determined by another court;
2. whether the proceedings constituted an action which “could not succeed and lead to no possible good”;
3. whether the proceedings had been brought for an improper purpose, including harassment and oppression of other parties;
4. whether there was a “rolling forward of issues into subsequent actions”, such as repeatedly seeking High Court judicial review proceedings to frustrate the outcome of Circuit Court decisions;
5. the whole history of the matter, including whether there was a pattern of unmeritorious conduct on the part of the appellant;
6. whether there was a failure of an appellant to pay the respondent’s costs of previous unsuccessful proceedings; and
7. the conduct of the appellant in persistently pursuing unsuccessful appeals.

Supreme Court

Ms Justice Elizabeth Dunne in the Supreme Court, in upholding the decision of the Court of Appeal to make an Isaac Wunder order, in summary concluded the following:

• The courts have a variety of remedies available to it to stop litigation that is vexatious or an abuse of the process of the courts to include:
  • striking out the vexatious pleadings;
  • striking out abusive proceedings; and
  • making Isaac Wunder orders where there is repeated unmeritorious litigation by a party to proceedings.
• Isaac Wunder orders should be made sparingly and a court must act proportionately. This is because of the importance of the constitutional right of access to justice. That being said, an order will not prevent a party from enjoying their right of access to justice, given that the effect of an Isaac Wunder order is to restrict a party bringing a new application or proceedings without leave of the court. It is not a restriction on issuing proceedings in a stateable case.
• Isaac Wunder orders will only be made after a party has made “a number of unmeritorious applications have been made”.
• There is no bar to making an Isaac Wunder order in family law proceedings but the best interests of the child must be taken into account.
• A structured approach to making Isaac Wunder orders could be considered by the legislature and/or the Rules Committees of the courts.
• Making Isaac Wunder orders, being part of the inherent powers of the court to prevent an abuse of process, are not confined to the High Court, Court of Appeal and Supreme Court. The Circuit and District Court may make Isaac Wunder orders subject to certain limitations including:
  • These courts do not have jurisdiction to oust the jurisdiction of any courts of greater jurisdiction. For instance, the District Court may not make an order restricting the issue of proceedings in the Circuit Court, and the Circuit Court may not make an order restricting the issue of proceedings in the High Court.
  • An order if made will be valid throughout the country as a whole and not limited to the geographical jurisdiction of the court that ordered it. However, as a party can only initiate proceedings in a venue which has jurisdiction to deal with the matter, an Isaac Wunder order will only be effective in the Circuit or District in which the relevant court would otherwise have jurisdiction to deal with the matter.
• In addition to the power to make an Issac Wunder order, there are a range of other powers at a Court’s disposal to safeguard the administration of justice when presented with a serial litigant or someone who disrupts or prolongs proceedings on a repeated basis to include:
  • where an application for leave to apply for judicial review is brought on a basis which is factually misleading, an application to set aside the grant of leave may be appropriate; and
  • the availability of the DAR as an important safeguard to ensure that parties do not misrepresent what occurred in court on a previous occasion.

Other steps taken by the judiciary

It is clear that disruptive conduct has become more prevalent in court, with the President of the High Court issuing a Notice following consultation with the President of the Court of Appeal.

The Notice indicates that disruptive behaviour includes issuing proceedings that are improperly repetitious of previous proceedings or are oppressive, frivolous or vexatious.

The Notice goes on to reference the types of orders the Court may make regarding disruptive conduct, including excluding the person from a physical court room and restricting them from issuing proceedings generally without prior consent of the High Court.

Following the Supreme Court’s decision in M v M, on 28 January 2026, the President of the High Court issued Practice Direction 135 on Isaac Wunder/Litigation Restriction Orders: Procedures and Related Matters.

The Practice Direction re-iterates the inherent jurisdiction of the High Court to consider granting an Isaac Wunder order, either where an application has been made to the Court, or where the Court considers of their own motion that an Isaac Wunder may be appropriate.

Comment

The Supreme Court’s decision is a timely reminder that Irish Courts possess a suite of powers to curtail serial or disruptive litigation.

By endorsing the use of an Isaac Wunder order in appropriate cases, even in sensitive circumstances such as family law proceedings, the Court strikes an important balance between individual rights, and the collective interest of litigants and the administration of justice.

While these orders are exceptional, parties who are subjected to oppressive or vexatious litigation should bear in mind the availability of an Isaac Wunder order, with the Supreme Court providing welcome clarity on when and how it can be effectively and proportionately deployed.

This article first appeared on the Mason Hayes & Curran website.