Constitutional bodies are those established by specific provisions in the Constitution of India. - The Election Commission of India is established under Article 324 of the Constitution. - The Goods and Services Tax Council is established under Article 279A of the Constitution. - Metropolitan Planning Committees are provided for under Article 243ZE of the Constitution. NITI Aayog, on the other hand, was established by a resolution of the Union Cabinet in 2015, replacing the Planning Commission. It is an executive body and not a constitutional one.