Port Walkout Treated Gingerly by Critics : Labor: D.A. investigators seeking to serve a warrant were cornered by about 300 members. Union local shut down Los Angeles and Long Beach harbors for 13 hours.

Even those who know the waterfront are sometimes amazed how powerful and clannish longshoremen can be. Wednesday night, several hundred union members in Wilmington proved that reputation, closing the nation’s busiest port over the attempted arrest of one member for nonpayment of child support.

The 13-hour walkout, criticized only privately Thursday by port officials, shippers and some union members, began after two investigators for the Los Angeles County district attorney’s office entered the union’s dispatch hall at 5:30 p.m.

Within minutes of their arrival, the investigators were cornered by about 300 angry longshoremen, a union official was arrested for inciting a riot, and the International Longshoremen and Warehousemen’s Union, Local 13, closed the Los Angeles and Long Beach harbors, idling 33 ships carrying tens of millions of dollars in cargo.

“It’s crazy,” said Los Angeles Police Capt. Dick Bonneau. “I mean, my gosh, they had a warrant and a union hall is not a sanctuary against arrest.”

The walkout ended at 8 a.m. Thursday for the 5,000-member union, a local known to even other ILWU affiliates as hot-headed and stubborn. “This sort of thing wouldn’t happen with the other locals,” said one union official, who requested anonymity. “They just don’t act like Local 13.”

While union officials refused comment, police and others familiar with the incident said it began almost the moment that Jeff Oh and Ron Hobson, two district attorney’s investigators, walked into Local 13’s dispatch hall. The hall is where the dockworkers gather before being dispatched to jobs. It is a place where strangers are eyed suspiciously. The front entrance sign warns: “I.L.W.U. MEMBERS ONLY.”

Oh and Hobson never saw that sign, entering the hall from a side door with an arrest warrant for Roy Neal, 49.

The first person to approach them was the union’s sergeant-at-arms, John Louis Nappi who, Hobson and Oh said Thursday, made it clear they were not welcome.

One dispatcher got on the hall’s microphone and ordered Oh and Hobson out. “You two cops sitting on the back bench, get out. You don’t belong here,” Oh quoted the dispatcher as saying. Oh said he and Hobson stood up to leave, but they were blocked by most of the 300 union members present.

“We were surrounded and everyone was looking at us. They were shouting, ‘Get the hell out,’ ” said Oh, 28. “We hear that all the time in our jobs. But not from that large a crowd.”

Unable to leave, the investigators rushed to a tiny office in the hall. “. . . Then the crowd started yelling louder and pushing on the door, trying to get to us,” said Oh, who along with Hobson is a former sheriff’s deputy.

While Hobson phoned for help, Oh held his body against the door. “They were kicking the door, trying to break it down. There was no way out,” Oh said.

“If somebody would have gone through the door, we would have been forced to use deadly force to protect ourselves. It had gotten that bad,” said Hobson, 29.

With sheriff’s deputies and Los Angeles police en route, the investigators made one last plea to calm the crowd. “The guy who started the whole thing came around . . . and we told him he was going to jail for inciting a riot,” Oh said. “I could tell by his face he knew he’d created a monster.”

When authorities arrived, the investigators were escorted outside and Nappi, 65, of San Pedro, was arrested. Union members, agitated that their leaders ordered them home, closed the ports until morning.