What are the rules governing international use of water areas to dump used spacecrafts from orbit or launch trajectory.
(source: Wikipedia / Nasa)
This would apply to rocket stages, boosters, tanks, decommissioned satellites, space station returning cargos, etc. Some may burn during re-entry, some may not, and some may be dumped before reaching any orbit.
Is that formally allowed to dump space stuff into oceans, are there specific areas empty of human activities reserved for such purpose?
Is there any international agreement on what could return to Earth (e.g. hazardous propellant like hydrazine)