Hello Stu,
As a rule (article 110), navy ships (of any nation) have the right of visit and may board your ship if they
suspect your ship is engaged in piracy, slave trade, illegal broadcasting (!), has no nationality (art. 92.2), or hides her flag being in reality of the same nationality of the navy ship herself.
The definition (art. 101) of piracy is not very restrictive "
any illegal acts of violence or detention, or any act of depredation,...." and cannot be the fact of a naval ship. (They commit illegal acts, collateral damage, errors, mistakes, war crimes, acts of war ...).
Idem slave trade (Spambot, children, ...).
And of course, Captain Kool is quite right, Art. 92.1 says:
Ships shall sail under the flag of one State only and, save in exceptional cases expressly provided for in international treaties or in this Convention, shall be subject to its exclusive jurisdiction on the high seas.So, if you are suspect,
your freedom of the seas could change if you damage the paint of the boarding party!
Regards,
Luc