Sonowal took the issue of Bangladeshi infiltration to the Supreme Court. By its judgement dated 12 July 2005, the court struck down the Illegal Migrants (Determination by Tribunal) Act, 1983, as unconstitutional and termed Bangladeshi infiltration an "external aggression" and directed that "the Bangladesh nationals who have illegally crossed the border and have trespassed into Assam or are living in other parts of the country have no legal right of any kind to remain in India and they are liable to be deported."