law: 7. Formation of the Union territory of Arunachal Pradesh.-
  On and from the appointed day there shall be formed a new Union territory, to be known as the Union territory of Arunachal Pradesh, comprising the territories which immediately before that day were comprised in the tribal areas specified in Part B of the table appended to paragraph 20 of the Sixth Schedule to the Constitution (but excluding the areas covered by notification No. TAD/R/35/50/109, dated the 23rd February, 1951 issued by the Governor of Assam under the proviso to sub-paragraph (3) of the said paragraph 20) and known as the North-East Frontier Agency and thereupon the said territories shall cease to form part of the existing State of Assam.