The feud between Governor Spitzer and the Republican Senate majority leader, Joseph Bruno, has yielded at least one happy result for taxpayers: a new ethics policy that frowns on public officials using state aircraft for political purposes.

Until yesterday, rules governing the use of the executive chamber’s air fleet had been virtually nonexistent in Albany, a permissive environment that allowed governors and other state leaders to zip to fund-raisers and other political events on the wings of the executive chamber’s aircraft and on the backs of taxpayers.

The lack of clear guidelines also led to accusations of abuse, most recently in July, when Mr. Spitzer ordered Attorney General Cuomo to investigate whether several helicopter flights taken by the governor’s chief legislative foe, Mr. Bruno, were improper.

The governor’s move against Mr. Bruno backfired disastrously several weeks later, when Mr. Cuomo issued a report that cleared the 78-year-old Senate leader of any wrongdoing but chastised the Spitzer administration for directing state police to dig up and re-create Mr. Bruno’s travel records in an effort to catch him misusing state aircraft.

While absolving Mr. Bruno, Mr. Cuomo’s report called for a “rigorous” state aircraft policy that would better protect state resources.

Weighing in for the first time on the issue with a formal advisory opinion, the New York State Ethics Commission ruled that public officials are prohibited from using the aircraft unless the “primary” reason for the trip is a “bona fide state purpose.” Officials also are now required to reimburse the state for parts of trips that are not related to official business.

The New York Sun reported on Tuesday that the Ethics Commission had never rendered a written opinion on the use of state aircraft. The closest thing to policy ever formulated by the commission was a 2001 statement from a spokesman that referred to informal oral advice given by its executive director to the Pataki administration in 1995.

The executive director at the time, Richard Rifkin, who is now a special counsel to Mr. Spitzer, apparently told Governor Pataki that he could freely use the aircraft for trips that contained at least one public purpose.

The commission yesterday also ruled that officials must disclose their itineraries, whose contents will now be generally made available through New York’s Freedom of Information Law.

The Ethics Commission, which is led by a Spitzer appointee, John Feerick, a former dean of Fordham Law School, is also conducting a preliminary review of the Spitzer administration’s actions against Mr. Bruno to determine if any ethical violations were committed.

The opinion may help Mr. Spitzer to present his administration’s actions in a more favorable light. After all, the central element of the administration’s plot against Mr. Bruno was capturing and releasing to the press the Senate leader’s itineraries. Under yesterday’s ruling, such records — as long as they don’t pose a security risk — will now be available to the public.

A spokeswoman for Mr. Spitzer said the administration would not comment on the opinion until it completed reviewing it.

Mr. Cuomo, a Democrat, said in a statement he was “gratified” by the commission’s new aircraft guidelines, which he said would “prevent the abuse of taxpayer funds.” He also said he preferred a “bright line” policy that would prohibit “any non-official usage,” thereby minimizing “any ambiguities in the policy.”

A spokesman for Mr. Bruno said the Senate favors legislation that would ban public officials from conducting any political activity on trips using state aircraft. Mr. Bruno has said he is no longer using the governor’s air fleet.

Advocates for stricter ethics guidelines in Albany cheered the commission’s ruling, while cautioning that the new policy had a few soft spots.

The opinion, for instance, states that public officials would be violating public officers law if “the State business proffered as the reason for the trip is nothing more than a pretext to permit the State official’s use of State aircraft for non-State activities, particularly partisan political activities.”

The document, however, does not provide any definition for what constitutes a “primary” purpose.

Mr. Cuomo’s report found that on some occasions when Mr. Bruno flew on a state helicopter between Albany and New York City, he conducted a minimal amount of official business and spent more time attending political fund raisers and dinners.

For elected officials, New York’s executive air fleet has long been a lavish privilege and a focal point of political attacks.

In 1994, Mr. Pataki assailed Governor Cuomo for shuttling family members on state aircraft and flying to rallies and fund raisers. The New York Times noted in a 1995 article that “Air Pataki” replaced “Air Cuomo.”

As governor, Mr. Pataki also allowed family members to fly along and was harshly criticized by his 2002 Democratic challenger, H. Carl McCall, for his frequent use of state aircraft and taxpayer-funded chartered flights.