flag of convenience

Short definition from Wiktionary

Noun

1. 1
   Registration of a ship in a country chosen for its low taxes, permissive regulations, etc.
2. 2
   The flag flown by a ship so registered (corresponding to the country of registration).
3. 3
   Use of a particular location or jurisdiction as one's nominal base of operations in order to take advantage of favorable laws and regulations or to avoid restrictions on one's operations.