Core Legal Answer & Context: The classical definition of International Law, which primarily focused on states as the sole subjects and treaties/customs as the main sources, has indeed become largely redundant. Contemporary international law has evolved significantly, recognizing a broader range of actors and sources, and addressing a wider array of issues.

Relevant Statutes and Sections:

1. Article 38(1) of the Statute of the International Court of Justice (ICJ): Lists traditional sources (treaties, custom, general principles, judicial decisions, teachings). While foundational, it doesn't fully capture modern developments.
2. UN Charter: Recognizes the role of international organizations.
3. International Human Rights Covenants: Grant rights directly to individuals, making them subjects of international law.

Important Landmark Cases:

1. Reparation for Injuries Suffered in the Service of the United Nations (ICJ Advisory Opinion, 1949): Recognized international organizations as subjects of international law, capable of possessing international rights and duties.
2. Nuremberg Trials (1945-46): Established individual criminal responsibility under international law, a significant departure from the state-centric view.

Clear Conclusion: The classical definition is outdated. Modern international law encompasses a diverse range of subjects (states, international organizations, individuals, NGOs, multinational corporations), broader sources (including 'soft law'), and a wider scope of issues (human rights, environmental law, international criminal law). This evolution reflects the complex and interconnected nature of global society, rendering the narrow classical definition inadequate.