When a federal grand jury in Arizona indicted two ranchers last week on charges of robbing and beating three Mexican aliens, some Justice Department officials used terms like "creative" and "imaginative" to describe the legal theory.

For the first time in a brutality case the Hobbs Act, a statue to prosecute organized and white collar crime, was used instead of the usual civil rights statues in indicting Patrick and Thomas Hanigan.

Some department attorneys familiar with the case, however, have grumbled privately that the department appears to bending the rules in going after brutality cases that have become an important political issue in the Hispanic community.

Using the Hobbs Act in a robbery case violates Criminal Division policy, and Assistant Attorney General Philip B. Heymann says he pointed that out in discussions of the Hanigan case several months ago.

Drew S. Days III, assistant attorney general in charge of the Civil Rights Division, says the case fit the usual standards: that the evidence showed a violation of civil rights, and that it was determined the federal government had the power to intervene.

The case illustrates the department's increased interest in pursuing Hispanic cases.

Al Perez, a Washington attorney for the Mexican-American Legal Defense Fund says flatly that this organization believes Justice wouldn't have prosecuted the Hanigan case except for long and vocal Hispanic demands.

"Even if they were forced into the case by the Hispanic pressure, brought in kicking and screaming, the indictment shows they were finally convinced some action was required," Perez said.

In 1977 the Hanigans were acquitted on state charges stemming from the same incident. The Justice Department decided then that no federal statue applied because the basic civil rights laws required either that the alleged victim of brutality be a citizen or that the alleged attacker be a law enforcement official.

Hispanic groups kept up their campaign, however, filing briefs that suggested the Hobbs Act approach and even filing suit unsuccessfully to try to force action. The case was reopened and went to a grand jury last summer, after an internal department debate over whether the Hobbs Act should be applied.

Attorney General Benjamin R. Civiletti, who faced opposition from Hispanic groups during his confirmation hearings last summer said in a phone interview last week that he didn't feel political pressure played a part in the decision to prosecute the Hanigans.

"I think an accurate assessment is that in those cases where there are substantial regional or community-wide problems, we will take a hard look to see if a sound case can be developed, rather than simply take a pedestrian look at it," he said.

"If in the end, we cannot make cases on the facts, we will not bring them," he added.

Indeed, the Justice Department has taken considerable heat, and Civiletti has been praised within the department, for refusing to allow prosecutions in a couple of other controversial cases involving Hispanics.

Last year while he was deputy attorney general, Civiletti resisted Hispanic a Dallas police officer in connection with a five-year old shooting. h

Griffin B. Bell, then the attorney general, had decided that no prosecution was warranted because the state had already convicted the officer. President Carter asked Civiletti to review the case while Bell was out of the country and though a White House aide was later quoted as saying, "You just cost us Texas," Civiletti agreed there was no case.

Last summer, Civiletti decided after painstaking research not to authorize prosecution of Texas jailers involved with the death of another Mexican-American. After ordering a fourth pathologist to review the circumstances of the death. Civiletti joined other department attorneys in deciding the evidence was insufficient to warrant prosecution.

Federal review of crimes usually prosecuted by the states dates back to a Bell decision in 1977 reversing previous policy. Beginning then, Justice has reviewed cases where state prosecutions were non-existent or frivolous.

The first case brought under this "dual prosecution" policy saw a Texas state marshal tried and sentenced to life in prison for a shooting, after having been put on probation by a state trial.

Vilma Martinez, president of the Mexican-American Legal Defense Fund, called it ironic that some Justice lawyers feel the department is too zealous in its pursuit of Hispanic civil rights cases.

"I'd like to be out of business, but we still have a long way to go," she said. She said the department ought to prosecute other Hispanic cases, draw up guidelines on the use of deadly force, and educate the public on the issues. Martinez voiced disappointment that Civiletti didn't discuss Hispanic civil rights problems in a recent speech to the International Association of Chiefs of Police in Dallas.

Civiletti is moving on other fronts to carry out his nomination-hearing pledge to be responsive to Hispanic concerns. He is hiring a Hispanic special assistant who has been an assistant U.S. attorney in Houston, and he is organizing a Hispanic advisory committee.