Al-Nahl (The Bee) Chapter 16: Verse 43 (partial)
The Quranic principle of consultation although primarily addressed to the Muslims, does not exclude the non-Muslim citizen from the scope of its application, nor indeed from the ranks of the consultative assembly (majlis al-shura). Thus, the non-Muslim may be elected to the consultative assembly, and may represent his or her own community. The above verse authorizes non-Muslim participation in consultation pertaining to community affairs outside of the scope of religion.
The right to criticise government leaders and express an opinion critical or otherwise, in public affairs, or indeed to formulate a response to a statement or opinion expressed by another individual is, once again, the right of every citizen, Muslim and non-Muslim alike.
However, matters which pertain to the dogma of Islam, or those which are regulated by the direct authority of the Quran or Sunnah, criticism, either from Muslims or non-Muslims, will not be entertained, as personal or public opinion does not command authority in such matters. Islam is basically a religion of authority, and the values of good and evil, or rights and duties are not determined by reference to public opinion, or popular vote, although these too have a certain role to play in the determination of the rulings. But, this need not diminish in any material sense the substance of the freedom of expression that the individual must enjoy under the shariah.
"Freedom of Expression in Islam" - Mohammad Hashim Kamali, pp. 106, 107