Electronic Transactions Act (ETA): Singapore's primary legislation governing electronic transactions and digital signatures. Even for handwritten documents, understanding this act helps determine when handwritten vs electronic authorizations are legally acceptable.

Evidence Act (Chapter 97): Governs the admissibility of documents in Singapore courts. Specifies requirements for document authenticity and how documents can be proven in legal proceedings.

Contract Law (Common Law): Fundamental principles governing formation of valid agreements, including clear intent, scope, and duration of authorization. Based on Singapore's common law system.

Stamp Duties Act: Determines whether stamp duty is payable on the authorization document, depending on the nature and purpose of the authorization.

Mental Capacity Act: Ensures the person giving authorization has the legal and mental capacity to understand and execute the document.

Powers of Attorney Act: Relevant if the authorization amounts to a power of attorney, specifying formal requirements and scope of authority that can be delegated.