THE SWEEPING INDICTMENT on federal racketeering charges of 19 Maryland-based members of Mara Salvatrucha, or MS-13, is a rare piece of good news in the fight against this region's most violent Latino street gang. Originally fashioned as a legal weapon to fight the Mafia, the federal racketeering law known as RICO, which federal prosecutors in Maryland used to charge the men, has proved more versatile than anyone imagined. Now RICO -- the Racketeer Influenced and Corrupt Organizations Act -- is becoming a powerful tool to combat street gangs.

And not a moment too soon. Like la Cosa Nostra, Latino gangs such as Mara Salvatrucha are extravagantly violent organizations that use nearly hermetic secrecy, codes of honor and cultural exclusivity to erect barriers that can be difficult for law enforcement to breach. So far law enforcement has managed only to chip away at MS-13, which until now has been described as maddeningly scattered, dispersed into independently directed cliques. Departing from that conventional wisdom, the Maryland indictment, though still sealed, apparently depicts MS-13 as more sophisticated and structurally coherent than previously believed. According to the charges, MS-13 factions from different regions hold summit meetings, stay in touch by cell phone and pay dues that support other gang members imprisoned in this country and in El Salvador. Perhaps the group's organizational heft will provide other federal prosecutors with additional openings to mount legal attacks on MS-13 here and in other regions where it is active.

The indictment announced this week suggests that the new U.S. attorney in Maryland, Rod J. Rosenstein, recognizes the magnitude of the growing threat the gang poses in the Washington suburbs. So does the dramatic manner in which the arrests were carried out: Some 320 law enforcement officials from federal and local agencies fanned out at 1:30 a.m. Thursday to arrest nine of them; the others were already in custody on state charges. That sends a message to MS-13, and so will aggressive prosecution of the indicted men, some or all of whom may face life in prison. The Maryland suburbs, like Northern Virginia, have watched with alarm as the gang's members have sliced each other up with knives and machetes. Now law enforcement authorities are striking back, and not a moment too soon.