Promoters of a controversial pipeline that would carry natural gas from the Canadian border to Long Island scored a major and perhaps decisive victory yesterday when a federal administrative law judge supported them on every point against a challenge raised by opponents.

Judge Walter J. Alprin ruled that the 370-mile, $582 million Iroquois pipeline is needed to meet energy requirements of the Northeast and that its proposed rate structure is acceptable. Because all the Canadian gas to be carried by the pipeline is needed to meet projected demand, he said, the project would not be unfair to domestic producers.

His ruling clears the way for the Federal Energy Regulatory Commission to give final approval to the project at a meeting in November. The project's opponents -- domestic gas producers, New England fuel dealers and environmentalists in New York and Connecticut -- have until Oct. 3 to file objections to the ruling, but it seems unlikely that they will persuade the commission to reject it.

The commission gave preliminary approval to the pipeline in July, but ordered the judicial proceeding to give the project's opponents a last chance to make their case.

"It's a grand slam," said Iroquois spokesman Gary Davis. He said it was "very important to provide comfort to people concerned about these issues," including the project's financial backers and Canadian gas producers and regulators, who reportedly have had second thoughts about it.

Paul Hilliard, chairman of the Independent Petroleum Association, an organization of U.S. gas producers that has fought vigorously against Iroquois, said, "We are very disappointed in the judge's findings of facts." Hilliard said his organization "intends to file objections to the judge's determinations, and we are hopeful that the commission will maintain an open mind. We are not done yet."