HE'S the best-known ex-secret operative in the world. It's the boyish grin, the quizzical look, the hair, the assurance he wears like a uniform now that he doesn't wear uniforms anymore. He's so American he met his wife at the mall. He was bumbling, which she enjoyed."We think we're so cool. And they catch us at it," Oliver L. North says. He means wives, not special prosecutors. He smiles, and suddenly it all comes back: the hearing room, the klieg lights, the swearing-in with his arm upraised and all those medals, the defiance and the charm, the bad jokes about shredding. Ollie-mania made him a hero to conservatives and a black villain to liberals, which suggests neither group listened to what he actually said - but that's another story. Now he's back, big time. "Nightline," "Donahue" ("not an altogether pleasant experience"), all the trappings of a book tour with bodyguards. The last of those pesky convictions has been thrown out of court, on grounds that the congressional Iran-contra hearings tainted the testimony at his trial. He's a free man. Got off on a technicality, you say? He believes that's the way the American legal system works. "I am exonerated," he says. "I know it grates at some of your colleagues." Grates? Really? That disagreement with Donahue must have gotten out of hand. And it's true that his National Press Club appearance was a little rocky, yet North did make that crack about the press being not a pack of jackals, but "a bunch of individual jackals." The crowd didn't take it as a joke. At least there aren't camera crews camped outside his home anymore. At the height of Iran-contra interest they were there even on Christmas morning, when North's daughter Dornin felt sorry for them and brought out a plate of cookies. Recently North met a cameraman who told him the rest of that story: The assembled media were at first suspicious of the gift. They fed the first few cookies to the North dog, Max. "Max is alive today and fatter than ever. He still provides unwilling security for the family," says his owner. If truth be told, North is hard to talk to. He's charming - that's not the point. The problem is what to ask. Think about it. First the congressional hearings, then the trial, then the appeals, now the bulk interviews. He's answered more questions in the past six years than anyone in America. He's got it down. The real scandal aficionados, the reporters who come in with piles of documents and arrange them on the table before they begin, and ask things like "did Ghorbanifar become upset about the Second Channel before, or after, your eighth meeting with The Nephew?" haven't made a dent. He's not going to tell them anything new. He expresses regret, it was wrong to mislead Congress and so forth, but he was only acting under authorization. After all these years he's still not going to be anybody's fall guy. MUCH has been made of his assertions that Ronald Reagan must have known of the Iran-contra connection. North argues that he's been saying that all along, and it shouldn't be news to anyone. That's true, but the sight of one conservative icon dumping on another still comes as a surprise. North feels Reagan pitched him over the side, and he resents it. In fact North doesn't call himself a Republican. He's campaigned for Democrats, he says, and his daughter interned for Democratic Sen. Ernest F. Hollings of South Carolina. He refers to his politics as "traditional, focused on common-sense values." In specifics, he sounds like a conservative populist, the flip side of Democratic Sen. Tom Harkin of Iowa. Term limits are his big issue. "Across the board, both parties, both houses, I do not believe that the Congress today reflects the values of the American people," he says. He will no longer campaign for any candidate who doesn't support such limits. He doesn't agree with the argument that term limits aren't necessary because voters can just refuse to reelect incumbents if they want. Sitting legislators have unfair advantages in attracting money and press coverage, he says. He doesn't agree that congressional reelection machines in fact depend on doing what the people want. "A lot of them flat out lie," he says. "The people are told different things about what they really do." Is revenge at work here? A little pay-back for those six days of being grilled on national TV? North denies it. Then he mentions that old saying about not getting mad, but getting even, and smiles one of those gap-toothed grins. North says he doesn't know if now he's going to fade away. He routinely denies any intention to run for office himself, but talks about a lunch with a prominent Virginia power broker. Any future public life would have to have the approval of his "best friend" (read: his wife) and kids. He wears suits now. He's gained a little weight. Ollie the lieutenant colonel is gone. What sort of symbol will he be next?