The Centre has authorised no person to hold dialogues with North-East insurgents on its behalf and negotiations, if any, would be tripartite in nature involving the state government, official sources said here on Friday.‘‘The Centre has not authorised any person to negotiate with the militants on its behalf. Law and order, being a state subject, should be dealt with by the state government,’’ Deputy Prime Minister L.K. Advani told Chief Minister D.D. Lapang in Delhi yesterday.‘‘None from outside would be allowed to interfere with internal affairs of the state without the knowledge and proper authorisation of its government. The state has the sole responsibility of maintaining law and order and the Centre will continue to render all assistance and support,’’ an official release here today quoted Advani as saying.