Section 27(2) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(2)The Captain of a ship, or the senior officer of more than one ship, visiting a foreign port where there is a fort or saluting battery, or where a ship of the nation may be lying shall salute the national flag with 21 guns, on being satisfied that the salute will be returned. A salute shall not be fired when the ship is passing through territorial waters with no intention of anchoring, or making fast in any way, in them, even if a saluting station is passed, unless unusual circumstances make it desirable. The salute shall be fired on each occasion that a ship visits a foreign port, except that of a ship leaving port temporarily, when, by agreement with the local authorities, the salute on her return may be dispensed with.
