The issues in the Straits of Malacca are no longer related to international law but increasingly to geopolitics. It is about maritime powers imposing their will on coastal states and their excuse to enforce jurisdiction in national waters.
Under international law, piracy is a universal crime — a crime against humanity — whereby universal jurisdiction applies. The courts of the states that seize a pirate may decide on the penalties.
I suspect talk of instability, terrorism and bomb-floating vessels are excuses by some maritime powers and institutions to claim a stake in the governance of the strategic waterway.
I also suspect that all the loose talk is intended to provide legitimate excuses for external powers to intervene with their navies to rewrite the rules of engagement in straits used for international navigation. The Malacca Straits is their pilot scheme.
On the point of maritime terrorism as the current equivalent of piracy, a noted authority on international law cautions that "Terrorism cannot by traditional forms of argument be shown to be criminal whatever its quality might be in the municipal law of the state or groups of states the terrorists are trying to destabilise".
It would not surprise me if a big accident were to be staged in the Straits of Malacca by those with sinister designs to provide evidence, to legitimise fears for their impending threat scenarios.Of course, when a huge amount of world trade flows by your door, and "robbers" keep popping out to hold up participants in the trade, you might expect the robbed will eventually look to you to stop the robbers. And if you fail to do so, they might do it for you.
It is hardly incumbent of them to take another path, as suggested here:
My advice to those who fear "pirates" in the straits is that they should bypass it; use instead alternative routes like the Straits of Sunda and Lombok or, in future, the proposed pipelines across the Isthmus of Kra.