The system is in force today in four Northeastern states Arunachal Pradesh, Nagaland, Mizoram and Manipur. In addition, the inner line permit is required to enter the islands of Lakshadweep.
No Indian citizen can visit any of these states unless he or she belongs to that state, nor can he or she overstay beyond the period specified in the ILP.
The concept comes from the colonial area. Under the Bengal Eastern Frontier Regulation Act, of 1873, the British framed regulations restricting the entry and stay of outsiders in designated areas. This was to protect the interests of the the Crown.
The inner line permit for the foreign tourist is called the Protected Area Permit, which is different from the inner line permit for domestic tourists.
According to the Foreigners(Protected Areas) Order 1958, all the land that comes within the inner line of a particular state, especially the North-East state, is declared a protected area and requires a Protected Area Permit to enter.