The U.S. State Department has pieced together a patchwork of extracts from international agreements relevant to aspects of the case, but it has not offered a definitive text to back its case that the Chinese may not board a military spy plane which made an emergency landing on its territory.

The EP-3 plane, on a surveillance mission along the Chinese coast, landed on Hainan island in southern China in distress after a mid-air collision with a Chinese fighter.

The United States bases its argument on the principle that military aircraft count as "state aircraft," like warships which are not liable to search in international waters.

The other principle, also enshrined in the Chicago Convention of 1948, is that a signatory country must provide assistance to planes in distress "as it may find practicable".

An older customary principle is that when vessels in distress seek shelter in the nearest port, the local government should treat them as though they are practicing the right of innocent passage through territorial waters, experts said.

Ruth Wedgwood, an expert on international organizations and law at the Council on Foreign Relations, said she found the argument convincing and the practice wise, in that it would endanger lives if military personnel feared taking shelter.

"If they were permitted to land, the burden is on the Chinese authorities to prove that the United States has waived the immunity of the plane," she said.

CONSULAR ACCESS

But several legal experts on Tuesday rejected the U.S. argument that these fragments add up to a clear case against China's treatment of the EP-3 plane.

"There is no authority for the proposition that a spy plane is like the sovereign territory of the United States," said Francis Boyle, professor of law at the University of Illinois.

"China has the right to open an investigation and is bound only by the rules on consular access."

The Chinese authorities allowed consular access to the 24 crew members on Tuesday but they have not said if or when they will release the crew or the plane.

John Quigley, professor of law at Ohio State University, said military planes in international airspace, like warships in international waters, clearly had sovereign immunity.

"But I have never heard of applying that concept inside a state, except in the case of embassies and diplomats, which are covered by the Vienna Convention," he said.

"Certainly if there was suspicion of a crime aboard, it wouldn't have any protection."

One analogy offered by Pentagon spokesman Craig Quigley was that of a NATO defense minister visiting the United States and parking his plane at Andrews Air Force Base.

The other analogy was that of a U.S. warplane in distress over Bosnia that landed in Slovenia. The Slovenian government allowed the United States to repair the plane and fly it out.

INNOCENT PASSAGE

But in both these cases the two governments are friendly and have an interest in maintaining good relations.

The U.S. case is weakened to some extent by a provision in the Convention on the Law of the Sea that vessels "collecting information to the prejudice of the defense or security of the coastal state" are not entitled to innocent passage within territorial waters, usually defined as 12 miles off shore.

In 1981, for example, Sweden held for 10 days a Soviet submarine which ran aground in its territorial waters. The Swedes suspected it of spying but the Russians said it had merely made an innocent navigational error.

In 1991, during an air campaign led by the United States, the Iraqi government sent hundreds of warplanes to neighboring Iran for shelter from U.S. bombing. Iran kept them, without any outcry from the international community.

Another precedent, but relevant only for its influence in U.S. law, is that of the Exchange, an American schooner seized by the French navy and converted into a warship.

When the ship later took shelter from bad weather in Philadelphia harbor, the original owners staked a claim. But the U.S. Supreme Court ruled in 1812 that the ship enjoyed immunity from U.S. jurisdiction.

(Agencies 04/04/2001)