Innocent Passage

2016: IRGC Releases US Marines after Receiving Apology:

Iran's IRGC Navy detained two US navy combat vessels and 10 marines in the Persian Gulf on Tuesday. Tehran released the sailors on Wednesday and after it was proved that the US troops were in Iranian waters unknowingly.

According to an Iranian video, the sailors were fed and treated well:

Under international maritime law, the U.S. vessels were entitled to pass through Iranian waters under the theory of "innocent passage" as set out in United Nations Convention on the Law of the Sea (emphasis added):

Article 17

Right of innocent passage

Subject to this Convention, ships of all States, whether coastal or land-locked, enjoy the right of innocent passage through the territorial sea.

Article 18

Meaning of passage

1. Passage means navigation through the territorial sea for the purpose of:

(a) traversing that sea without entering internal waters or calling at a roadstead or port facility outside internal waters; or

(b) proceeding to or from internal waters or a call at such roadstead or port facility.

2. Passage shall be continuous and expeditious. However, passage includes stopping and anchoring, but only in so far as the same are incidental to ordinary navigation or are rendered necessary by force majeure or distress or for the purpose of rendering assistance to persons, ships or aircraft in danger or distress.

Article 19

Meaning of innocent passage

1. Passage is innocent so long as it is not prejudicial to the peace, good order or security of the coastal State. Such passage shall take place in conformity with this Convention and with other rules of international law.

2. Passage of a foreign ship shall be considered to be prejudicial to the peace, good order or security of the coastal State if in the territorial sea it engages in any of the following activities:

(a) any threat or use of force against the sovereignty, territorial integrity or political independence of the coastal State, or in any other manner in violation of the principles of international law embodied in the Charter of the United Nations;

(b) any exercise or practice with weapons of any kind;

(c) any act aimed at collecting information to the prejudice of the defence or security of the coastal State;

(d) any act of propaganda aimed at affecting the defence or security of the coastal State;

(e) the launching, landing or taking on board of any aircraft;

(f) the launching, landing or taking on board of any military device;

(g) the loading or unloading of any commodity, currency or person contrary to the customs, fiscal, immigration or sanitary laws and regulations of the coastal State;

(h) any act of wilful and serious pollution contrary to this Convention;

(i) any fishing activities;

(j) the carrying out of research or survey activities;

(k) any act aimed at interfering with any systems of communication or any other facilities or installations of the coastal State;

(l) any other activity not having a direct bearing on passage.

Were the U.S. Navy vessels engaged in "innocent passage?" Certainly appears that way.

Did the Iranians have the right to investigate the situation? Sure.

Did the Iranians seize the opportunity to inflate the situation through their ham-handed media efforts? Of course, that's what they do.

Is it worth going to war over? No, it barely scratches the surface of notice compared to the other stuff the Iranians are up to.

UPDATE: Why do I feel that the Iranians had the right to investigate? Because of the long list of things that would make a passage not "innocent." A nation has the right check on transients who are not "expeditious" in their transits or why bother with all the exceptions? Does that investigation including searching the suspect vessels for contraband and the like? Now, here we get into the sovereign right of flagged warships of another country  . . .  which is a much bigger issue.

UPDATE2: You might recall the 1981 incident of a Russian submarine that asserted it had "inadvertently" grounded in Swedish waters and how the Swedes treated that incident:

In October 1981, the Soviet submarine S-363 accidentally hit an underwater rock about 10 kilometres (6.2 mi) from the main Swedish naval base at Karlskrona, surfacing within Swedish waters.[3] The boat's presence coincided with a Swedish naval exercise, testing new equipment, in the area. Swedish naval forces reacted to the breach of sovereignty by sending an unarmed naval officer aboard the boat to meet the captain and demand an explanation. The captain initially claimed that simultaneous failures of navigational equipment had caused the boat to get lost (despite the fact that the boat had already somehow navigated through a treacherous series of rocks, straits, and islands to get so close to the naval base).[3] The Soviet navy would later issue a conflicting statement claiming that the boat had been forced into Swedish waters due to severe distress, although the boat had never sent a distress signal, and instead attempted to escape.[4]

The Soviet Navy sent a rescue task force to the site in Sweden, commanded by vice-admiral Aleksky Kalinin[5] on board the destroyer Obraztsovy; the rest of the fleet was composed of a Kotlin-class destroyer, two Nanuchka-class corvettes and a Riga-class frigate. Sweden's centre-right government at the time was determined to safeguard Sweden's territorial integrity. As the Soviet recovery fleet appeared off the coast on the first day, a fixed coastal artillery battery locked onto the ships, indicating to the Soviets that there were active coastal batteries on the islands. The fleet did not turn immediately and as they came closer to the 12-mile (19 km) territorial limit the battery commander ordered the fire control radar into top secret war mode, turning the radar signal from a single frequency to one that jumped between frequencies to stay ahead of enemy jamming. Almost immediately the Soviet fleet reacted and all vessels except a heavy tugboat slowed down, turned, and stayed in international waters. Swedish torpedo boats confronted the tugboat, which also left.[citation needed]

The Swedes were determined to continue investigating the circumstances of the situation. The Soviet captain, after a guarantee of his immunity, was taken off the boat and interrogated in the presence of Soviet representatives.[4] Additionally, Swedish naval officers examined the logbooks and instruments of the submarine.[4] The Swedish Defence Research Agency also secretly measured for radioactive materials from outside the hull, using gamma ray spectroscopy from a specially configured Coast Guard boat. They detected something that was almost certainly uranium-238 inside the submarine, localized to the port torpedo tube.[3] Uranium-238 was routinely used as cladding in nuclear weapons and the Swedes suspected that the submarine was in fact nuclear armed.[3] The yield of the probable weapon was estimated to be the same as the bomb dropped over Nagasaki in 1945. Although the presence of nuclear weapons on board S-363 was never officially confirmed by the Soviet authorities,[6] the vessel's political officer, Vasily Besedin, later confirmed that there were nuclear warheads on some of the torpedoes, and that the crew was ordered to destroy the boat, including these warheads, if Swedish forces tried to take control of the vessel.[7]