Step 1: Understanding the Act of State doctrine.
The doctrine of Act of State in tort law means that certain acts performed by a sovereign state or its agents, within its jurisdiction, cannot be challenged or interfered with by the municipal courts of other countries. This is especially relevant in international law, where the actions of sovereign states are generally immune from judicial scrutiny by foreign courts.
Step 2: Explanation of the options.
- (a) An act of the sovereign power of a country, that cannot be challenged, controlled or interfered with by municipal courts: This is correct, as the classical doctrine of Act of State grants immunity to such acts.
- (b) An act of the Judiciary of a country: This is not the correct answer, as the judiciary does not typically deal with "Acts of State."
- (c) An act of the sovereign power of a country, that can be challenged: This contradicts the doctrine, which does not allow such challenges.
- (d) None of the above: This is incorrect, as option (a) is correct.
Step 3: Conclusion.
Thus, the correct answer is (a) an act of the sovereign power of a country, that cannot be challenged, controlled or interfered with by municipal courts.