Assume, for a moment, that an official in the government of Iraqi President Saddam Hussein wants to come to the United States and meet with the families of American hostages.

Bush administration officials believe that allowing this official into the country for such a meeting could jeopardize U.S. foreign policy interests. Should the Iraqi official be denied a visa?

Yes, say congressional supporters of a new immigration bill, pointing to language that allows the administration to exclude foreigners under these and similar circumstances.

But civil liberties groups are protesting that some provisions in the bill go too far in allowing the U.S. government to bar foreigners on the basis of their beliefs or associations.

Moreover, the American Civil Liberties Union argues that unless a person is entering the country to commit a crime, foreign policy considerations should not keep that person out.

"Nobody should be denied a visa on foreign policy grounds," said Morton H. Halperin, director of the ACLU's Washington office.

This hypothetical scenario falls into a group of issues still rankling several weeks after passage of the sweeping revision of immigration law.

Most provisions contained in the legislation, which expands by nearly 40 percent the number of immigrants allowed to enter the country, elicited support from across the political spectrum.

Among the most popular components of the bill was its elimination of several Cold War-era prohibitions, which had permitted the government to keep out foreigners on the basis of their ideology or homosexuality.

The provisions, part of the 1952 McCarran-Walter Act, had been used to exclude celebrated politicians and writers, including Carlos Fuentes and Graham Greene.

But retained in the legislation were a handful of sections allowing the United States in certain circumstances to bar foreigners on the basis of their "beliefs, statements or associations."

Those exceptions were the result of congressional compromise, with Sen. Alan K. Simpson (R-Wyo.) fighting for the restrictions and more liberal members of Congress, including Rep. Barney Frank (D-Mass.), agreeing to the language with the understanding that the provisions be used sparingly.

Despite assurances that Congress will carefully monitor the administration's use of the exclusions, that they remain in the bill has raised complaints from the ACLU and other lawyers' groups.

"At some point, this power will be utilized and people will suffer ideological exclusions," said Arthur C. Helton, project director with the Lawyers Committee for Human Rights.

The legislation permits exclusion on the basis of ideology or association if the secretary of state personally determines that the admission of that person "would compromise a compelling United States foreign policy interest."

Under the bill, the secretary of state must report his reasons to the relevant congressional committees.

"We really think it's a reasonable provision," said Dick Day, an aide to Simpson. "We look at it as something that's going to be used very infrequently. We're giving our State Department a tool to protect a compelling foreign policy interest."

"We intend this to be very narrowly and carefully defined," said an aide to Sen. Edward M. Kennedy (D-Mass.), a sponsor of the legislation. "If it's abused, we will know it."

But the provision, according to Sen. Daniel Patrick Moynihan (D-N.Y.), "revives a McCarthy-era relic in the very year that the Cold War came to an end."

Moynihan, who three years ago pushed through an amendment prohibiting exclusion of foreigners on the basis of their beliefs, argued that the restrictions in the new bill were a retreat he called "unnecessary and profoundly disappointing."

In the three-year history of his amendment, he said in a statement, there was no evidence "that it caused any problems which justify retreating on this important is- sue."

When it comes to foreign political candidates or officials, as in the hypothetical case of an Iraqi official, the U.S. government cannot prohibit entry solely on the basis of ideas, but must also cite the office itself as grounds for foreign policy concerns.

While the new bill eases prohibitions against Communist Party members, it denies entry to party members unless they have immediate relatives in the country or have denounced their party ties.

Helton argues that this provision "can only be explained as a legacy of the Cold War."

While congressional sponsors argue that the ideological exclusions will rarely be used, Helton contends that where the power exists, it will be exercised.

"You can be sure that, someday, you will see these powers being reached for and exercised," he said. "There is no reason to look at our border in an ideological fashion."