THE foreign powers intervening in the domestic politics of Haiti these days are none other than members of the century-old bastion of Latin American noninterventionism: the Organization of American States.The world's oldest organization of nations, the OAS has long been termed an "ineffectual debating society" and the "graveyard of diplomats." But after persistent diplomacy since the Sept. 30 coup, the OAS last week won the Haitian parliament's agreement to hold talks on the restoration of constitutional government. The talks would be held outside Haiti and include President Jean-Bertrand Aristide. The OAS's uncharacteristically ambitious, unified effort to restore democratic order in Haiti, observers say, is an example of a new vitality in relations in the Western Hemisphere. The earthquake in world affairs of the last few years - including the collapse of the cold war, the emergence of regional trade blocs, and the democratization of all but a couple of small nations in the hemisphere - has jostled the region into a little-noted but widely felt new order of its own. The convergence of political and economic change is dramatic, says Peter Hakim, staff director of the Inter-American Dialogue. "What the OAS is able to do now is largely a reflection of improved relationships between the US and Latin America. With the decrease of sensitivities to intervention and more willingness to defend values like human rights, all of a sudden the US and Latin America find themselves on the same side," says Mr. Hakim. "One key is the end of the cold war as a security issue. The other key factors are the trend toward democratic governments in Latin America and [President Bush's] Enterprise for the Americas Initiative [free trade and investment proposals], which is an invitation for stronger relations with the rest of the hemisphere," Hakim explains. The volatile issues dividing the region in the recent past invariably cast the heavy-handed yanqui North as pressuring the weaker, poorer South to do its bidding. The OAS was in the awkward position of defying the United States or playing handmaiden to its policies. Most North-South clashes revolved around the principle of nonintervention. Latins harbored hostility, suspicion, and defensiveness over the anticommunism that drove US policy. Argentina, for example, would not budge from opposition to the US ouster of Gen. Manuel Antonio Noriega from Panama in 1989, even though General Noriega allegedly had had ties with Argentine coup-plotters. Argentina's new perspective on nonintervention is a striking contrast, says Mario del Carril, former press aide at the embassy here. Argentina is now one of the strongest voices for a multilateral peacekeeping force in Haiti. The OAS's quick and continued resolve to seek reinstatement of President Aristide stems from the organization's "Santiago Commitment to Democracy and the Renewal of the Inter-American System." Adopted last June, that document rejuvenated the OAS. In another era, its unprecedented automatic mechanism to deter illegal action against democratically elected governments and its provisions to promote cooperation in the hemisphere might have been seen as just so much rhetoric. "But it's not rhetorical because it has been applied in Haiti, and that has suprised many people," says Heraldo Munoz, Chile's ambassador to the OAS. "The commitment was a declaration with a plan of action of priorities for the 1990s, democracy being most fundamental and including drug trafficking, environment, trade and investment, and poverty." OAS Secretary-General Joao Clemente Baena Soares notes that the Haiti initiative is not the only precedent being set under the Santiago Commitment. Even before that, he adds, the OAS had begun election monitoring programs for newly democratic nations, and it has been involved in repatriating former contra rebels into Nicaragua. Another change is the more highly skilled Latin American representatives in the marbled corridors of OAS headquarters here, observers say. Governments are sending diplomats who are younger and better-versed in modern diplomacy. Many are political appointees rather than career diplomats, which means they are more directly connected to power back home, notes a South American diplomat. The US has shown a more serious interest in the OAS too. For the first time since 1982 it paid its $40 million OAS dues in full last year and began paying up on its arrears of $48 million. The 1989 appointment of Ambassador Luigi Einaudi as US representative to the OAS is seen as a signal that the US is taking the organization more seriously, say observers. He is the first Spanish speaker and bona fide Latin Americanist in recent memory to hold the position, they note. Indeed, many diplomats at the OAS note that the US suddenly has "started listening." Citing a "new spirit" characteristic of the changing times, Mr. Einaudi describes last month's ad hoc meeting of foreign ministers called to deal with the crisis in Haiti: "In 90 minutes I listened to 18 speakers. Can you believe that? ... They want to get their points across but they've learned to get them across without all the fanfarroneria [bluster] and references to [Latin American hero Simon] Bolivar.... It's a cultural revolution." Einaudi notes that beyond rhetoric is the new context of agreement shared by the 34 member nations. "There is no longer automatic hostility. When we were having the problems with Nicaragua or Panama, half the sessions of the permanent council were screaming sessions...," observes Einaudi. "But it's a totally different context when you get together and figure out, what are we going to do collectively about the situation in Haiti? What are we going to do to help advance the GATT talks? How can we do something on the environment that makes sense? Suddenly there are positive issues where you can get some c ooperation."