Are these straits international waters?
Indonesia claims Malacca strait as a territorial sea.
"It is one of the busiest ocean highways in the world. An estimated more than 41,000 ships pass through the South China Sea each year - more than double the number that crosses the Suez Canal and nearly treble the number of ships that use the Panama Canal.
Its closure could generate a massive increase in freight rates worldwide and hit bulk shipments hardest."
In short, global economic disaster could ocurr if the strait was closed.