Adv. Don Justin Mahon SC

The seminal reported case dealing with insider trading in South Africa. Don Mahon SC appeared together with JJ Brett SC in proceedings that established foundational principles governing the Directorate of Market Abuse's powers and the rights of persons subject to investigation under the Securities Services Act and its successor legislation. The judgment remains the primary authority on insider trading enforcement in South Africa.

The first Supreme Court of Appeal judgment to address the test for the granting of a business rescue order under Chapter 6 of the Companies Act 71 of 2008. Don Mahon SC appeared on his own, against two silks — JJ Brett SC and A Subel SC — each of whom was assisted by a junior. The judgment established the interpretive framework that all subsequent courts have applied when considering business rescue applications and is cited as the foundational authority in virtually every contested business rescue proceeding.

A novel question of company law: whether a company incorporated outside South Africa and registered as an external company under the Companies Act is entitled to utilise the business rescue provisions of Chapter 6. The applicant, CMC, was a long-established Italian construction company that had encountered severe financial difficulties and sought business rescue protection in South Africa, where it had significant operations and creditors.

Don Mahon SC appeared in both the High Court and the SCA proceedings together with Brett SC. The SCA held that an external company as defined is not a 'company' for the purposes of Chapter 6 and accordingly cannot benefit from the business rescue machinery. The judgment is the leading authority on the availability of business rescue to foreign-incorporated entities and has practical significance for international businesses operating in South Africa.

Don Mahon SC appeared as counsel before the Commission of Enquiry into Allegations of State Capture, chaired by Deputy Chief Justice Zondo (as he then was), representing amongst others the South African Ambassador to the Netherlands, Bruce Koloane. The Commission was one of the most significant public inquiries in post-apartheid South Africa, examining systemic corruption at the highest levels of government and the private sector. Appearing before the Commission required engagement with complex factual records, multiple represented parties, and a quasi-judicial process of national consequence.

Related High Court proceedings in the cannabis litigation, preceding the Constitutional Court judgment in Prince. Don Mahon SC appeared as lead counsel in the Gauteng Division, laying the foundation for the constitutional challenge that was ultimately confirmed by the Constitutional Court. The matter involved complex constitutional arguments concerning the right to privacy, the limitations clause, and the relationship between criminal law and constitutionally protected personal autonomy.

A challenge to the constitutional validity of legislation criminalising the private possession, use and cultivation of cannabis by adults in their private capacity. The matter was argued before the Constitutional Court, where Don Mahon SC appeared as lead counsel without a leader, against teams led at various stages of the litigation by prominent senior counsel. The Constitutional Court handed down a unanimous judgment striking down the impugned provisions as an unreasonable and unjustifiable infringement of the right to privacy under section 14 of the Constitution.

The judgment is the leading constitutional authority on the limits of State regulation in the private sphere and has been cited extensively in subsequent constitutional litigation. It is one of the most significant reported judgments in Don Mahon SC's career — and among the relatively rare instances of an advocate appearing without a leader in the Constitutional Court.

An appeal in the Supreme Court of Appeal concerning whether section 218(2) of the Companies Act 71 of 2008 provides a basis for a shareholder to claim individually for loss suffered as a result of diminution in share value caused by directors' breaches of duty — a direct claim that would otherwise be barred by the rule against reflective loss. The matter involved claims of R721 million and R1.3 billion respectively and was contested by senior counsel including Wim Trengove SC, Chris Loxton SC and Ian Green SC.

The SCA confirmed that the rule against claims for reflective loss was not abolished by the 2008 Companies Act and laid down principles that now govern the relationship between section 218(2) and the common law in this field. Don Mahon SC was involved in the matter from the outset and appeared at various stages with a series of silks, including in the SCA proceedings with Subel SC.

An appeal before a full bench of the Supreme Court of Appeal — presided over by the President of the SCA — on the question of whether a valid customary marriage came into existence between the late South African musician Jabulani Tsambo (HHP) and the respondent, and specifically whether the requirement of a formal handing-over ceremony (ukumekeza) had been satisfied or could be waived by agreement between the families.

Don Mahon SC appeared for the deceased's family, leading Cecilia Marule in both the High Court and the SCA proceedings, opposed by Advocate A Bester SC. The matter attracted national attention and raised foundational questions about the evolution of customary law as a living legal system. The SCA held that ukumekeza could be waived by agreement in appropriate circumstances, confirming the dynamic character of customary law. The judgment is a significant authority on the Recognition of Customary Marriages Act and on the courts' approach to evolving customary practice.