Posts on dual/multiple citizenship may be found here.

Dual citizenship or nationality and multiple citizenship or nationality (dual/multiple citizenship) is a way of describing the situation where a person holds the citizenship or nationality of more than one state under the law of those states. In other words more than state claims a person as belonging to it under its law.

Many states are intolerant of Dual/multiple citizenship. Some states prohibit its own citizens from the acquiring the citizenship of additional states and will take measures to deprive them of its own citizenship where there that prohibition is violated.

Some states require those seeking to acquire its citizenship to renounce any other citizenships held. Other states require their minor citizens to renounce any additional citizenships held on attaining the age of majority in order to retain its citizenship. In some cases  states permits dual/multiple citizenship though only with citizens from certain other states.

Where a person holds the citizenship of more than state, each state of citizenship  may decline to recognise the citizenship of that person when or or she is within its territory or is otherwise subject to its jurisdiction. Typically  access to consular services and diplomatic protection is restricted.

A person who holds more than one citizenship may seek to hold passports from each state. Issues often arise as to the exercise of citizenship rights (such as voting rights) in these circumstances as well as the performance of the duties (such as military service) attendant upon each citizenship.

Posts on dual/multiple citizenship may be found here.