The American Civil Liberties Union is not likely to hold a dinner dance in honor of Rudolph Giuliani, the vivid United States attorney for the Southern District of New York. In pursuing mobsters (including the heads of five "families" at one crack), tax-fraud acrobats and predatory politicians, Giuliani pays no heed to Louis Brandeis' warnings about the corroding effect on the Fourth Amendment of electronic surveillance. He is also fond of "proactive" investigations. Or as Abscam's Mel Weinberg once put it, "Let's put out the honey pot and see who'll come for a taste."

Giuliani, moreover, has greatly irritated defense attorneys by his penchant for press conferences at which indictments are worded in drum-rolling language more suited to announcements of convictions. Because Giuliani is easily, even eagerly, available to the press, his critics charge that he is creating momentum for a political career along the lines of such gangbusters of the past as Thomas Dewey. Unlike the stiff Dewey, however, Giuliani is informal and sometimes downright rebellious. In 1984, for instance, when the Reagan administration declared war on those of the disabled too handicapped to work by denying hundreds of thousands of them Social Security benefits, federal courts in various circuits restored benefits to some who had sued and, in the process, harshly criticized this abuse of the helpless. The administration countered by ordering its attorneys to follow a policy of "nonacquiescence." When someone with a disability won a victory in federal court, the government refused to apply that ruling to similar cases. Each new complaint would have to be tried again with resultant anguish and expense.

Giuliani refused to go along with "nonacquiescence." He said: "We have not defended cases in the past by disregarding the law of this circuit, and we will not do so in the future."

Recently, I asked Giuliani what he thought about the frequent excoriations of the Miranda decision by the boss of all federal law-enforcement bosses, Edwin Meese. One of the attorney general's gentler descriptions of Miranda is "infamous." He doesn't go for the permissive nonsense that a suspect is no more than that. To the attorney general, once you're a suspect, there's a strong presumption that you're guilty; otherwise why would you be a suspect?

Giuliani did not tap dance around the question. "Miranda is not something we should be contesting," he said. "If you want people to waive their rights, it's equitable that they know what their rights are. Everybody understands Miranda; it's easy to apply, and it works well."

The U.S. attorney for the Southern District has also ventured into a mine field that most prosecutors prefer to avoid -- medical and hospital malpractice. Testifying before a New York hearing on the subject held by City Council President Andrew Stein, Giuliani emphasized that the trouble with private lawsuits is that they often end up with a settlement, the amount of which is sealed by the court, so that "any doctor can buy secrecy, or any institution can buy secrecy."

Accordingly, "there is an area here of almost blanket immunity (from exposure) because criminal prosecution rarely if ever happens. In part that's because prosecutors -- federal, state and local -- are afraid to enter this area because they give it a kind of religious mysticism that they don't give to legal questions, financial questions or political questions where, in fact, they are called upon to make qualitatively the same kinds of difficult, sensitive judgments."

As always, Giuliani is full of ideas about what should be done. He would like to apply the federal civil rights statutes to malpractice cases. One of those cil rights, he points out, is the right to live. Giuliani also suggests strongly that a record be available to professional boards and prosecutors of each malpractice complaint and its disposition in the history of every doctor and hospital. It's "intolerable," he says, that a patient, as of now, has no access to that information.

Meanwhile, as Giuliani keeps preparing indictments in the near-epidemic corruption scandals in Democratic New York City, a powerful upstate Republican, Warren Anderson, majority leader of the state Senate, has ventured to make political hay by calling for a special commission to explore the cesspool. Giuliani, a Republican, straight-armed Anderson, accusing him of trying to make a "partisan issue" of this serious business.

Sen. Daniel Patrick Moynihan (D-N.Y.) said a few days ago that whatever his party's fortunes in the nation, he always wins his own elections. The odds may be the other way if the energetic, not quite predictable Mr. Giuliani runs against the discursive philosopher in 1988.