Ethics law restrictions on a Massachusetts Port Authority board member and Teamsters leader may play a role in future representation of constituencies at Massport, officials said.

The conflict-of-interest limits placed on George W. Cashman, president of Teamsters Local 25, came to light last week after the union chief supported several job actions affecting Logan International Airport, which Massport operates.Mr. Cashman has been forthright about backing a Teamsters clause that guarantees the right to participate in sympathy strikes as part of a contract under negotiation with Orlando-based Signature Flight Support Corp.

Mr. Cashman has said his members would not cross picket lines in the event of a strike against an airline that could prevent Signature from refueling aircraft. Teamsters also observed "informational" pickets posted at Logan terminals last Wednesday in a contract dispute between Massport and the International Association of Firefighters Local S-2.

But while the pickets did not stall traffic as feared on the busiest travel day of the year, the effects of the controversy may be long-lasting.

Kevin Kutz, a Massport spokesman, said Mr. Cashman has requested that the state ethics commission explain its guidelines under the conflict-of-interest law. According to one state official, the law would prevent Mr. Cashman from having any contact with Massport about his union's activities. So far he has not, Mr. Cashman and Mr. Kutz said.

The problem is the effectiveness of the traditional labor seat at Massport if Mr. Cashman is not allowed to represent his union at the authority. The limits also raise the question of whether vocal constituencies, such as neighborhoods opposed to airport development, will actually lose representation if their leaders are appointed to the board.

"Their response, once it's given, should have implications for every other board member and every member in the future," Mr. Kutz said, speaking of the ethics commission.

The outcome could derail legislation sponsored by James T. Brett, a state representative, that would add two Boston seats to the seven-member Massport board.

The new members, to be named by Boston's mayor, could be reluctant to serve if the ethics law prevents them from participating in decisions that may affect their neighborhoods or homes.

The "Catch-22" may also be a blessing for Massport's new Republican administration because of fears that the Brett legislation would swing the board's majority back to the Democrats. The guidelines could have the effect of giving Boston directors strictly limited voting rights.