Attorneys for Ronald L. Humphrey, the United States Information Agency employe charged with spying for communist Vietnam, yesterday asked that the United States be prohibited from ousting Vietnam's U.N. Ambassador from this country.

Humphrey's lawyer, A. Andrew Giangreco, yesterday filed a motion for a temporary restraining order barring the United States from expelling Ambassador Dinh Ba Thi because Thi "is and will be a material witness to this cause," the motion states.

Thi "is an unindicted conconspirator in this case," and "to permit this witness to be ordered out of the country will deprive (Humphrey) from the benefit of competent and material and relevant testimony and constitutes a clear violation of his constitutional rights," the motion states.

Giangreco could not be reached for comment yesterday but his cocounsel, John Grad, said the request, scheduled to be heard Friday in US. Distrrict Court in Alexandria, should open up new legal questions involving diplomats.

"This whole area of law is not well traveled," Grad said. "There aren't too many cases where the government" has expelled a high-ranking foreign government official. Thi's case is the first attempt to oust a U.N. ambassador from the United States.

A State Department spokesman said last night that the department was not notified of the court action.

"Our request for Ambassador Thi's prompt departure still stands," the spokesman said. ". . . I think he will be leaving very soon." The spokesman said Thi still is in New York.

Earlier yesterday another State Department spokesman laughed at Humphrey's lawyer's request and said, "I don't think that balloon is going to fly."

Typically, because of diplomatic immunity an ambassador cannot be forced to appear in court or be required to remain in a county, according to knowledgeable State Department officials.

U.S. gran jury named him as an unindicated coconspirator in the alleged plot to funnel classified diplomatic documents to the Hanoi government through an international espionage network.

At first, Thi said he would defy the U.S. order Last Sunday the Socialist Republic of Vietnam announced that it would recall him.

A foreign ministry officials in Hanoi said Thi was ordered home "because the U.S. government was hindering the activities of the Vietnamese U.N. chief."

Humphrey's motion is worded so that it does not request that the U.S. force Thi to remain, but seeks to prohibit the government from asking him to leave.

A spokesman at the Vietnamese Mission in New York hung up on a reporter who called to ask about the government's comment on the court filing.


Humphrey, of Arlington, and David Truong, the sone of a Saigon lawyer who once was a major political figue in Vietnam before the communist takeover in 1975, both were charged last week with stealing cables sent by overseas American diplomats to the USIA communications center where Humphrey worked.

Humphrey gave the cables to Truong who turned them over to couriers at clandestine locations for delivery to Hanoi officials in Paris, according to the indictment.

Last week The Washington Post reported that Humphrey's Vietnamese common-law wife has a 16-year-old son who is being held "a hostage" in Vietnam. Four other children and the woman, Chieu Thi Nguyen, also known as Kim Humphrey, got out of Vietnam this fall only after the intercession of German novelist and Nobel laurente Henrich Boll and diplomats from Sweden, Germany and the United States.

Humphrey himself appealed directly to the VIETNAMESE Embassy in Bonn when she was imprisoned in Saigon, according to government sources. She later was released and Humphrey was reassigned to Washington where he worked a nightshift in the USIA's operations center, a job that would have given him access to classified government cables.