The multicolored graffiti gangs paint on walls and streets in this city resemble scars on an old battlefield. They are thick on the borders of gang turf, where rivals spend sometimes bloody nights trying to paint out each other's slogans.

But Los Angeles officials have begun a novel attempt to use two obscure bits of civil law as a weapon to remove the graffiti, and perhaps also to ease the community fears and violence that often go along with the garish scribblings.

City Attorney Ira Reiner, who thought up the antigraffiti strategy, said in an interview that laws in other states could allow similar attacks on what is a common big-city blight.

Beginning Thursday, Los Angeles will file test suits charging three major gangs and their adult members with being "unincorporated associations" guilty of civil contempt by making a public nuisance.

"They think they are the authority in those neighborhoods, not the police," said Reiner, who sees the effort as much more than a neighborhood beautification project. He and other city officials said they had found almost unanimous support for an antigraffiti campaign when they circulated petitions in some affected neighborhoods.

"Many people didn't want to sign the petition simply because they said they were afraid of the gangs," Reiner said.

The police have counted 110 gangs in Los Angeles with a total estimated membership of 20,000, about 75 percent of whom are adults. Most are based in predominantly Latino or black neighborhoods, and their shootouts regularly bring death and injury.

Police officers say they hope to ease street violence because the spray-painted words often target victims, level provocative charges against rival gangs and incite turf battles. One gang is often tempted to see if it can spread its graffiti into another's territory.

"The criminal law is totally ineffective in dealing with the problem" of graffiti, Reiner said. Police rarely catch vandals painting their wall messages, as is necessary for successful prosecution.

The three gangs named in the suits--the Dogtown gang north of downtown, the Primera Flats gang south of downtown and the 62nd Street Crips in south-central Los Angeles--are particularly long-lived, well-structured organizations with a reputation for intimidating their neighbors through graffiti.

Reiner said he would attempt to prove that the graffiti are covered under a state law making certain signs and advertising a public nuisance. Then, in the most unprecedented and difficult part of the legal maneuver, he must convince a judge that the gangs are legal entities, "unincorporated associations," and thus can be sued and each of their members be made liable for other members' "tortious acts."

If convinced, the judge could order the gang members to clean up their graffiti, and if they don't, convict them of civil contempt and sentence them to five days in jail. After two or three such jail penalties without result, Reiner said, he could then ask a judge to put gang members under indefinite detention.

"As far as I know, this is the first time this has been tried anywhere," Reiner said, although many other states possess the nuisance laws and association rules which would apply.

In the District of Columbia, however, the plan would probably not work, according to D.C. police community relations Sgt. Wendell Huffstutler. What graffiti Washington has, he said, are rarely gang-related, but incited by local protests whose supporters are much more difficult to find and identify.