Any individual has the right to reside in, leave and return to the state of his/her citizenship. It is usually the state whose citizens his/her parents are and where he/she was born. In the case of stateless persons, it is the state of their habitual residence.
The immigrant is a person who has left his/her country in order to permanently settle in another state. Where people leave their state, they are called “emigrants”, and where they enter a foreign state, they are called “immigrants”. The reasons for immigrating into another state may vary – employment, setting up a family or education. Irrespective of the reasons, however, immigrants leave their country to settle in another state on their own will and by their own decision without being forced to do so by other individuals or factors.
By way of law the states are not under the obligation to receive individuals who are not their citizens on their territory. Immigration is limited to the requirement for certain reasons (grounds) to be available based on which the foreigner may be allowed to enter and stay for the purpose of permanent residence in a foreign state without being its citizen. This change of residence from one’s state into another one may take place only if the requirements, conditions and rules introduced by the laws of the latter are observed. These rules are referred to as an immigration regime.
While the immigration regime varies among states, there are several requirements that are universally valid across all states. The entry and stay in a foreign state cannot take place without a passport and a visa. Moreover, the national borders of a state must be crossed only at the points designated for that purpose (border crossing points) where an entry stamp is laid on the passport. A foreigner who has duly observed these rules is treated as a legal immigrant (regular immigrant).
If an immigrant has entered Bulgaria or another European state without a passport, a visa or has not entered via the points designated for that purpose, and has thus crossed the border without the permission of the border authorities, he/she is treated as an illegal immigrant (irregular immigrant).