Step 1: Understanding the scope of Article 253.
Article 253 empowers Parliament to make any law for implementing:
- Treaties
- International conventions
- Agreements with foreign governments
Step 2: Importance of Article 253.
Even if a subject falls under the State List, Parliament can still legislate when it is for fulfilling an international obligation.
Step 3: Why not the other options?
- Article 249 allows Parliament to legislate in national interest on State List subjects.
- Article 251 deals with inconsistency between Union and State laws.
- Article 255 deals with validity of laws requiring Presidential assent.
Thus, Article 253 is the only correct match.