In what circumstances does a warship have a right, under UNCLOS, to board a merchant ship on the high seas?

(2) the ship is engaged in the slave trade: (3) the ship is engaged in unauthorized broadcasting and the flag State of the warship has jurisdiction under article 109; (4 ) the ship is without nationality; or (5) though flying a foreign flag or refusing to show its flag, the ship is, in reality, of the same nationality as the warship.