The last time Keith Morris came to First Avenue howling out old Black Flag songs, he was on a fundraiser tour with the Rollins Band a decade ago to help exonerate murder convicts the West Memphis Three.

“We won that one,” Morris happily noted, referring to the reversal of that high-profile case.

Morris sounds equally convinced that he’s on the right side of a whole other legal battle with his latest tour. He and other former members of Black Flag will hit First Ave on Friday under the moniker FLAG, playing classic songs by the revered Los Angeles punk band.

“The energy level has just been insane,” Morris bragged.

Things have gotten crazy behind the scenes, too. Black Flag guitarist Greg Ginn — who owns the band’s name and its signature four-bar flag logo — sued his former bandmates last month for hewing too close to the original group, which he revived this year. He also sued Morris and Black Flag’s most famous ex-vocalist, Henry Rollins, over trademark issues.

“We’re getting ready to sink our teeth into a really big and ugly dispute,” Morris said. “There’s no road map for where this thing is about to go.”

Nothing was really mapped out for FLAG, either, Morris said. He and bassist Chuck Dokowski — both founding members of Black Flag in 1976 — were invited to perform some of the old songs at a street fest in 2011 by the L.A. noise-punk duo No Age. Soon thereafter, concert promoter Goldenvoice (see: Coachella Music Fest) invited Morris to its 30th anniversary party, where FLAG first performed.

“They wanted me to make a speech or something like that, but I don’t really make speeches, I do this,” recalled Morris, who after leaving Black Flag in 1979 went on to front another influential L.A. punk band, the Circle Jerks, and more recently formed the power-blasting quartet OFF!

The band “fell easily into place,” he said, with two other Black Flag alumni in tow: drummer Bill Stevenson and another of the band’s four ex-vocalists, Dez Cadena. Stevenson’s bandmate from the Descendents, guitarist Stephen Egerton, rounds out the lineup.

After that first, impromptu show, Morris said, “We really didn’t even talk about what came next. We all just kind of knew what we had to do. It was undeniable, after seeing the reaction from everyone over hearing these songs again, including a lot of 17-, 18-year-old kids who’ve never heard them live.”

On tour, the two vocalists each handle the songs they originally recorded, including Morris’ “Nervous Breakdown” and “Wasted,” and Cadena’s “Jealous Again” and “White Minority.” They also tear through “Rise Above,” “Gimme Gimme Gimme,” “My War” and other songs recorded when Rollins fronted the band in the early ’80s.

Recalling the 2003 West Memphis Three tribute tour with Rollins, Morris said, “Those shows were great, because Henry doesn’t go out and do something like that without rehearsing everything to perfection. And you know where he got that kind of hard-work ethic was from Chuck Dukowski. Chuck’s the guy that instilled that ethic in all of us.”

Friendship, money don’t mix

Riotous in tone with a snide underbelly that mocked conservative politics and xenophobia, Black Flag blazed the trail for other independent rock bands with incessant, grueling tours.

Ironically, Morris said he quit Black Flag because “I couldn’t stand all that damn rehearsing.” He also admitted, “I had my own issues, too,” referring to substance-abuse problems.

Morris started the band with Ginn, whom he met in high school in Hermosa Beach, Calif. Ginn soon launched SST Records, the celebrated indie label that also housed the Minutemen and Minneapolis’ Hüsker Dü, and later Sonic Youth and Dinosaur Jr. (The Hüskers crew has had its own disputes with Ginn, too, but things have smoothed out in recent years.)

“Greg was a pretty good friend of mine, but when business creeps into things — and money — people always show their true colors,” said Morris, who had only nice things to say about Ginn’s distinctive, screech-and-crunch performance style. “The guy created a new language on guitar. In that regard, we should shine every light on him.”

As always when lawyers get involved, though, Morris would not talk in specifics about the legal battle. The nearest he got was discussing FLAG’s legitimacy.

“We know what we’re doing is right,” he said. “We’re not calling ourselves ‘Black Flag.’ We’re not doing anything wrong. We’re not stupid. We know what we can and can’t do.”

Asked if the dispute with Ginn has soured the fun on FLAG’s tour, Morris replied, “You mean: Has it lessened the way we go about singing all these angry, ugly songs?”

His was a rhetorical question.