That's wrong. In peacetime, in international waters, ships are allowed to go where they please. That's the source of much of the naval jockeying during the Cold War - both sides were well within their rights. It was psychological gamesmanship. Neither side's officers were cleared to open fire (and would have faced sanctions if they had).
It should be interesting to find out if China's military officers have been given the discretion handed over the Imperial Japan's officers in the run-up to the Second Sino-Japanese War. Ultimately, the Chinese government may have handed control over the decision to go to war to a bunch of junior officers, in hopes of low-cost territorial gains.
Ok, so why did we fire on 4 North Vietnamese torpeodo boats which lead to escalation of war. And why did we shoot down that Iranian airliner and why did the russians shoot down KAL 007 ?