If one country tightened controls on ship breaking then, by the laws of capitalism, the work would just go to the next country with the lowest labour costs who has less overheads so can pay more to buy the ship from its owners in the first place.
Global(ish) controls mean temporary disruption to the status quo but hopefully eventual improvement of working conditions for the people doing the grunt work at the bottom.
Obviously China can't keep producing dirt cheap steel forever so ship breaking will bounce back, hopefully with slightly less misery for its employees.