Tribute or ‘poll tax’ is the payments that non-Muslims make to Islamic authorities. Payment of this ‘tax’ exempts the payer from military service.
Taxation and conscription are two functions of the modern national government. This issue is another where Islam is in conflict with the modern nation-state. Islam was designed as a system of governance long before the modern nation-state had evolved. Even if the laws of that government allow for this, it is a fact that the origin of this ‘law’ is the Koran. This is another example of nationalism taking a back seat to the ‘Nation of Islam’.
I place this issue at #2 in my list of reasons that Islam causes wars because this issue HAS triggered a war between the United States and Islam in the past. In 1804, a number of U.S. ships (Including a warship) were seized in the Mediterranean because the U.S. government refused to continue to pay ‘Tribute’. The battle cry in the US was "Millions for defense, not a penny for Tribute!" What was this all about?
For us, the issue was freedom of the seas. For the Muslim pirates, the lands surrounding the Mediterranean were ‘Muslim lands’. Most, if not all of the land that touched the Mediterranean were either controlled by Islamic authorities or else had been in the past. This made the Mediterranean an Inland Sea controlled by Islam, or Muslim ‘waters’. It was a stretch to charge Tribute for ships passing through these waters because the Koran speaks of land, not waters. Nor does the Koran speak of ‘passing through’. However, the nationalistic nature of Islam encourages this belief. After all, Tribute is a combination of two functions of government. This is one of the places where Islamic governance authority is in conflict with the authority of the nation-state. As a result, this issue has been a basic cause of war in the past and will continue to be so in the future.