Step 1: Understanding the Concept:
The question asks for the area of international law where the principle of "\textit{tabula rasa}" is applied. "\textit{Tabula rasa}" is a Latin term that means "clean slate."
Step 2: Detailed Explanation:
The "clean slate" or \textit{tabula rasa} principle is a doctrine in the law of State Succession. State succession concerns the legal consequences that arise when one state replaces another state in the responsibility for the international relations of a territory.
Specifically, the \textit{tabula rasa} principle applies to treaty obligations. As per this doctrine, a newly independent state (typically a former colony) is not bound by the treaties entered into by the predecessor state that formerly controlled its territory. The new state starts with a "clean slate" and is free to decide whether to adopt or reject the treaties of its predecessor. This principle is codified in the Vienna Convention on Succession of States in respect of Treaties (1978).
Universal succession is a different theory where the successor state inherits all rights and obligations, which is the opposite of \textit{tabula rasa}.
Step 3: Final Answer:
\textit{Tabula rasa} under International Law relates to State Sucession.