Msgr. Charles Fahey, chairman of the Federal Council on the Aging and a normally law-abiding man, appears to have averted--for the time being anyway--a threatened scrape with the law.

In the meantime, however, the Reagan administration has abruptly removed two-thirds of the council's members--and the gavel from Fahey's hand.

It's the latest episode in the ongoing saga of the preparations for the 1981 White House Conference on the Aging, already under fire for alleged attempts by the administration to stack the membership of committees and appoint a host of presidential ringers to keep the meetings from becoming a chorus of criticism of cuts in funds for the elderly.

This year, the council, an advisory body, has held two of the four annual meetings required by the Older Americans Act. Fahey scheduled a third meeting for the end of August before leaving on a trip to Europe last summer. He returned to find that the meeting had been canceled, without his knowledge or permission.

When he investigated, Fahey said he found the meeting was called off at the "very strong" suggestion of Dorcas R. Hardy, assistant secretary for human development services in the Department of Health and Human Services. "She had no right to do that," Fahey said, a fact he said Hardy conceded when they later discussed the matter.

Hardy explained in an interview that she wanted to postpone the meeting until the president could replace 10 members whose terms had expired, which she said she thought would take only a short time. The meeting was called off without Fahey's knowledge, she said, only after repeated attempts to contact him failed.

Fahey, who was appointed to the council by President Nixon in 1974 and has been twice reappointed, wanted the council to prepare an agenda for the agenda-less White House Conference on the Aging that will be held here at the end of the month. After several unsuccessful attempts to get the top echelon of the conference to agree, he said he thought that executive director Betty H. Brake had agreed to let the council frame an agenda.

Earlier this fall, Fahey had set another council meeting for Nov. 5 and 6 in Washington. Subsequently, he was contacted by Hardy, who told him that the council had financial problems (its budget was cut from $500,000 in fiscal 1981 to $200,000 this year) and that money for that meeting might not be available. A week after Hardy called him, they spoke again. Fahey recounted their exchange:

"She said, 'We can't find the money anywhere.' "

"I said, 'We'll have the money if we have to run a bingo game to get it.' "

In a subsequent conversation, Fahey said, Hardy admonished him that if he called the meeting without being able to pay for it, "I would be acting illegally. She said, you know, if I did it, I could go to jail. And I said, 'It would be an interesting thing to go to jail for.' "

Fahey said he was intent on having the council meet because if the White House Conference begins without an agenda, "it will be an absolute mess."

Although Fahey forged ahead and got council members to agree to forgo their per diem and honorarium for the time spent in Washington, two other incidents closed the matter. First, according to Fahey, Brake said she had not agreed to let the council propose a conference agenda. And second, a week before the council's scheduled meeting, the White House told 10 of the 15 members that their terms were up and that they would be replaced.

Council member Mary Marshall, the Democratic state delegate from Arlington, received a letter signed by E. Pendleton James, President Reagan's assistant for presidential personnel. He reminded Marshall that she had served past the expiration date of her term. "Pursuant to the direction of the president and to facilitate the appointment of your successor," James wrote, "this is to notify you that your appointment . . . will be terminated today. Thank you for your dedicated service. Please do not construe this as a reflection upon you personally."

Marshall said she felt the rapid firings were an effort by the administration to prevent the council from meeting before the White House Conference. "They don't know what they want on the agenda and they don't want anybody else deciding for them," she said.

Fahey, who will remain on the board but will be replaced as chairman by Adelaide Attard of New York, was more inclined to blame the sequence on "ineptness" rather than politics. "Given everything else about the conference they're screwing up, this is just another thing they're fouling up," he said.