If you have more than one nationality, it is not always clear what your rights are. For instance, your country of origin may require you to do compulsory military service. Some governments want to limit dual nationality as much as possible. If you have only one nationality, it will be clear what your rights are. That is why people who want to acquire some nationality through naturalization are, sometimes, required to give up their other nationality if possible. This is called the renunciation requirement. If you are foreign citizen and want to get Russian citizenship, you have to do renunciation. But if you are Russian citizen and want to get foreign citizenship (U.S. citizenship, for example), you can keep your Russian citizenship. In this case you will get dual citizenship.