A Louisiana parish's ordinance, designed to combat crime by drifters by requiring all new employes in the area to register with police, is being challenged in federal court here.

The ordinance, which went into effect last month in St. Mary Parish (county), was passed in the wake of the murders of five teen-agers in Morgan City earlier this year. All were believed to have been committed by a drifter.

Under the ordinance, anyone who wants a job-or anyone who wants to change jobs-has to fill out a form, by photographed and fingerprinted, and pay a $10 fee. The worker is then given a special laminated identification card, and his or her picture and prints are forwarded to the sheriff and to the FBI.

There is no penalty for a person who does not register, but any employer who hires an unregistered person may be fined more than $100.

The American Civil Liberties Union has challenged the ordinance in U.S. District Court in Lafayette, La., claiming that it violates workers' rights to privacy, travel and equal protection of the law.

It also "adversely affects" employers because it intimidates workers and makes them harder to obtain, says M. David Gelfand, a Tulane Law School professor who is representing the ACLU in this case.

Gelfand pointed out that over time almost everyone who lives in St. Mary Parish, about 63,000 persons, would end up registered, photographed, fingerprinted and carrying and ID card.

St. Mary Parish is in south-central Louisiana, and it is a center of the oil and natural gas industry-an industry that attracts many transient workers. In recent years, residents in Morgan City, the parish seat, claim these drifters have committed ghastly crimes, including sex killings, kidnapings and mutilations.

"The greatest problem we have is with the transients." said Morgan City Police Chief Randy Ratcliff earlier this year before the law was passed. A survey, he said, showed that two thirds of the persons arrested there are drifters and that 85 percent of them had police records.

"A policeman down here comes across every kind of human being that walks the face of the earth," said Morgan City policeman Jay Morell. "A lot of them don't even walk. They crawl."

One drifter in that city of about 20,000 inhabitants was Robert Carl Hohenberger, a fugitive from California who has been a suspect in several kidnapings, murders and rapes. He came to south Louisiana last year and became a machinist in an oil-related business.

Hohenberger, 35, whom his employer called "the nicest fellow I ever met in my life," was charged with murdering five teen-agers-four girls and a boy-in Morgan City between January and May. The bodies of two girls were found in a septic tank in May, and the boy was found buried in a shallow grave, but the other two kidnap victim are still missing.

Hohenberger case brought the matter of itinerants to a head. The Morgan City Council passed an itinerant-labor registration ordinance in June. A month later, the Louisiana legislature approved a law to enable six coastal parishes to set up itinerant registration systems. All the parishes involved attract large numbers of drifters who are drawn by the prospect of lucrative employment in the oil industry or a related enterprise.

St. Mary Parish's statute went into effect Nov. 1, and about 3,000 people registered in the first month, Ratcliff said.

When the law was passed, ACLU complained and announced that it would test the statute in court if it could find someone willing to file a test suite.

Such a person was Forrest Reubin, a VISTA worker recently transferred to Franklin, La. to work in a nonprofit organization that helps workers get jobs, housing and education.

Although the St. Mary Parish law has drawn ACLU's attention, it is not the first one in Louisiana. Plaque-mines Parish, which is southeast of New Orleans, adopted such a law in 1963 after a similar outbreak of crime. Like St. Mary Parish, Plaque-mines is a magnet for people seeking work in the oil industry.

"The minute we passed the ordinance, there was an exodus of these workers-all hitchhiking out of the parish," said Luke Petrovich, the parish's public safety director. CAPTION: Picture, John Romero of Red Rock, Okla., is fingerprinted preparatory to getting a job. UPI