Don’t know! Anything seems possible though. I found this.
The Right of Self Defense Under International Law
Under international law, merchant vessels and their crews have the right to carry arms for self-defense if that is required for the vessel to exercise its freedom of navigation. Self-defense measures include providing weapons and training to the crew and/or hiring armed guards to allow the vessel to navigate. The self-defense measures and their employment should be proportionate to the threat.
The right of freely navigating the ocean, and of self-defense, of repelling force by force was common to both vessels [warship and armed merchant vessel]2; but every hostile attack in a time of peace is not necessarily practical. It may be by mistake or in necessary self-defense or to repel a supposed meditated attack by pirates. It may be justifiable, and then no blame attaches to the attack…3
This customary international law has been codified in the United States for US vessels and crews in 33 USCS § 383 “Resistance of pirates by merchant’s vessels”:
The commander and crew of any merchant vessel of the United States, owned wholly, or in part, by a citizen thereof, may oppose and defend against any aggression, search, restraint, depredation, or seizure, which shall be attempted upon such vessel, or upon any other vessel so owned, by the commander or crew of any armed vessel whatsoever, not being a public armed vessel of some nation in amity with the United States, and may subdue and capture the same, and may also retake any vessel so owned which may have been captured by the commander or crew of any such armed vessel, and send the same into any port of the United States.4
The basic freedom of navigation is a cornerstone of the United Nations Convention on the Law of the Sea (UNCLOS) (1982). UNCLOS includes 158 state parties. The United States, a UNCLOS signatory, has affirmed that it is customary international law to which the United States adheres.5
UNCLOS provides that all states and the vessels that fly their flags enjoy the freedom of navigation in the Exclusive Economic Zone (EEZ) and on the high seas. Within territorial seas, up to 12 NM from the coastal baseline, vessels enjoy the right of innocent passage. UNCLOS also requires all states to cooperate in the suppression of piracy.6
If pirates attempt to deprive vessels of their right to exercise the freedom of navigation, the shipowner and the crew may take reasonable steps to defend the vessel and the crew while in the exercise of freedom of navigation.7 These measures, as part of the vessel’s legally required vessel security plan,8 may involve security guards and outfitting lethal and nonlethal weapons, fittings such as razor wire and armor, and equipment, as well as training crew members in the use of lethal and nonlethal measures in self-defense.
Under international law, warning shots do not constitute a use of force.9 A failure of the vessel to heed warning shots or other oral warnings justifies firing into the vessel’s rudder or propeller area/outboard engine if warning shots and oral warnings go unheeded.10
While these measures are not restricted outside of territorial seas, within territorial seas, to enjoy the right of innocent passage, the merchant vessel should not exercise or practice with weapons of any kind or undertake any threat or use of force against the sovereignty, territorial integrity or political independence of the coastal state.11