Related Rule
Ecuador
Practice Relating to Rule 37. Open Towns and Non-Defended Localities
Ecuador’s Naval Manual (1989) states:
Belligerents are forbidden to bombard a city or town that is undefended and that is open to immediate entry by their own or allied forces. A city or town behind enemy lines is, by definition, neither undefended nor open, and military targets therein may be destroyed or bombarded. 
Ecuador, Aspectos Importantes del Derecho Internacional Marítimo que Deben Tener Presente los Comandantes de los Buques, Academia de Guerra Naval, 1989, § 8.5.1.3.