China's Supreme Court said on Tuesday that people caught illegally fishing in Chinese waters could be jailed for up to a year, issuing a judicial interpretation defining those waters as including China's exclusive economic zones.
An arbitration court in The Hague ruled last month that China has no historic title over the waters of the South China Sea and that it has breached the Philippines' sovereign rights with its actions, infuriating Beijing which dismissed the case.
None of China's reefs and holdings in the Spratly Islands entitled it to a 200-mile exclusive economic zone, the court decided.
The Supreme Court made no direct mention of the South China Sea or The Hague ruling, but said its judicial interpretation was made in accordance with both Chinese law and the United Nations' Convention on the Law of the Sea (UNCLOS), under which the Philippines had also bought its case.
"Judicial power is an important component of national sovereignty," the Supreme Court said.
"People's courts will actively exercise jurisdiction over China's territorial waters, support administrative departments to legally perform maritime management duties ... and safeguard Chinese territorial sovereignty and maritime interests."
Jurisdictional seas covered by the interpretation include contiguous zones, exclusive economic zones and continental shelves, it added.
People who illegally enter Chinese territorial waters and refuse to leave after being driven out, or who re-enter after being driven away or being fined in the past year, will be considered to have committed "serious" criminal acts and could get up to a year in jail, the Supreme Court said.
"The explanation offers legal guarantees for marine fishing law enforcement," it added.
China claims most of the South China Sea, through which more than $5 trillion of trade moves annually. Brunei, Malaysia, the Philippines, Taiwan and Vietnam have rival claims.
China periodically detains fishermen, especially from the Philippines and Vietnam, and Chinese fishermen also occasionally get detained by other claimants in the SouthChina Sea.