Palestinian-Americans visiting the occupied West Bank have been prosecuted by Israeli security authorities on charges that they were members of ''illegal'' Palestinian organizations back home in the United States.
Sentences have been handed down in at least three such cases in Israeli courts in recent years, even though membership in any organization is constitutionally protected in the US, according to Israeli civil-rights lawyer Felicia Langer and officials at two Arab-American organizations in Washington.
They say at least two cases have arisen this year. And there are probably more, they add.
It is illegal in Israel to be a member of the Palestine Liberation Organization or to be a member of a group directly connected to the PLO. Israel claims the arrested Palestinian-Americans belonged to groups of the latter sort. The question is whether the authority of Israeli law extends over actions of American citizens committed in the US.
This practice of ''extraterritorial jurisdiction'' is mandated in Israel's so-called Offenses Committed Abroad Statute, which was passed in an attempt to head off terrorism in that country.
The State Department's 1983 human-rights report on the Israeli-occupied territories acknowledges the use of this statute, citing an example: ''An American citizen of Palestinian origin was sentenced to two years for activities in connection with a Palestinian organization in the United States which occurred only within the United States and which were not illegal in the United States.''
The identity of that Palestinian, presumed to be serving his sentence in an Israeli prison, is unknown to officials of the American-Arab Anti-Discrimination Committee and the National Association of Arab Americans, both in Washington. The State Department knows the identity of this person but cannot release it because of privacy laws, a spokesman said.
Felicia Langer, who is also vice president of the League of Human and Civil Rights, says she has had direct involvement with three cases of US citizens charged with being members of ''illegal'' organizations in the US. They are Sami Esmail of Michigan, who spent 10 months in an Israeli prison in 1978; Cherif Jabber Siam of New Jersey, who was arrested in Israel last January and is serving an eight-month prison term; and Mike Monsour of New Mexico, who was held for 22 days in April, before his release following congressional and State Department pressure.
''Every case, one after another, is the same,'' Ms. Langer says. ''You are seeing a pattern here.''
In each case, the defendant was held incommunicado for extended periods of time during which he was interrogated by Israeli security authorities. Each of the three men complain that during their interrogations they were subjected to physical and psychological abuse and that they were forced to sign a ''confession'' in Hebrew, which none of them speaks or understands.
Mr. Monsour and Mr. Siam complain that between interrogation sessions they were made to stand without moving for ''hours'' with their hands handcuffed behind their backs and their heads hooded. Monsour says he was told that once he signed the ''confession'' this treatment would stop.
These allegations are consistent with the types of abuses cited in an April 1984 report by Amnesty International, a human-rights organization, on torture worldwide. The report's section on Israel says that some security suspects arrested in the occupied territories ''have been hooded,
handcuffed, and forced to stand without moving for many hours at a time for several days.''
According to the report, ''The confession often constitutes the main body of the evidence against the accused in the (Israeli) military courts and so offers an incentive to investigating personnel to ill treat arrested suspects.''
A spokesman at the Israeli Embassy in Washington denied that Monsour or other security suspects had been mistreated: ''He [Monsour] was afforded the same treatment as anyone who is detained in Israel. Our system is well known to be humane without any use of torture or anything like that.''
Even though Israel eventually released Monsour, the spokesman said, the position of the Israeli government is still that he ''is a supporter and fund-raiser for the PLO in the United States and he was detained because the government had some suspicions concerning his activities.''
The spokesman added, ''He [Monsour] admitted in the investigation that he was connected to the PLO.''
James Zogby, executive director of the American-Arab Anti-Discrimination Committee questions why, if Israeli authorities had established a positive link between Monsour and the PLO, they found they had to interrogate him for 22 days.
''Obviously, we thought the charges were trumped up,'' says Steve Goldstein of New Mexico Rep. Manuel Lujan's office, which worked for Monsour's release.
An official at the State Department's Bureau of Human Rights offered a curt statement regarding the case: ''We have taken Mr. Monsour's allegations seriously and have conveyed our concerns to the Israeli authorities.''
Will there be an investigation?
''We are making no special review of it,'' the official said.
About US government interest in his case, Monsour says, ''If it was Sakharov or the Soviet Union they would do anything they could - but it was Israel.''
He adds: ''It is un-American to criticize Israel.''
The US government's position on Israel's Offenses Committed Abroad Statute and its ''illegal organizations law'' has generally been that the US can accomplish more by working in the political sphere than by directly challenging Israeli jurisdiction on legal grounds. A legal challenge might disrupt US-Israeli relations and reduce the effectiveness of US officials on the scene in Israel who deal with such cases, officials say.
A key factor is that US appropriations of foreign aid - $2.5 billion annually to Israel - are contingent by law on a human-rights record acceptable to Congress.
Israel is not alone in its claim of extraterritorial jurisdiction. Both Italy and West Germany have also moved in this direction as part of their efforts to fight domestic terrorism.
A State Department official characterized the American position this way: ''The Israelis have an interpretation that may not be the same as ours but it is a reasonable interpretation of the state of (international) law.''
According to Thomas Mallison, a law professor at George Washington University , ''The Israeli statute is a flagrant violation of international law. It is a contradiction of the basic principle of territorial jurisdiction - that a country has jurisdiction over its own territory.''
He adds, ''To my knowledge the US government has never protested the Israeli statute despite its actual impact on US citizens from time to time.''
Ron Cathell of the National Association of Arab Americans thinks it is ''very disturbing. It is as if we are going back 100 years and saying that an Arab-American is not worth as much as a non-Arab-American.''
He adds, ''I think it flies in the face of what this country is supposed to be all about.''