Five Northern Virginia beer distributors have filed suit in Alexandria Circuit Court, challenging state liquor regulations that bar them from entertaining their customers.

One of the distributors is Joseph M. Guiffre, a member of the Virginia Highway and Transportation Commission, who has been under investigation by federal liquor agents for suspected violations of similar federal laws.

The suit was filed shortly after the 1985 General Assembly approved legislation that allows the distributors to entertain, but a lawyer said the beer wholesalers are fearful state officials may try to prosecute them for expenses they incur before the new law becomes effective. The measure, which would probably be effective this summer along with most new legislation, has yet to be signed by Gov. Charles S. Robb, a spokesman said yesterday.

Guiffre, 50, owns the Anheuser-Busch distributorship in Springfield and has been under investigation since last May for allegedly violating federal liquor laws. The federal laws, adopted after Prohibition and similar to the Virginia regulations, ban wholesalers and breweries from inducing retailers to buy their brands by presenting them with gifts or money.

Federal investigators have said that Guiffre may have violated that law, which is designed to prevent certain wholesalers from gaining monopolies, by entertaining retailers at athletic events and concerts.

Guiffre, appointed by Robb in 1982 to the 10-member policy-making highway commission, holds one of the most sought-after political appointments in the state. He could not be reached for comment yesterday, but his attorney, David G. Fiske of Alexandria, said there was some "federal implications" in the lawsuit. Federal liquor authorities generally follow state rulings on liquor laws in their enforcement practices, the lawyer said.

Virginia long has prohibited wholesalers from entertaining restaurateurs or grocers in an effort to get them to carry a particular brand of alcohol, said Robert Grey, chairman of the Virginia Alcohol Beverage Commission. Those laws are designed "to maintain a healthy competitive environment" he said.

Any distributor who entertained retailers could face fines and lose his ABC license.

Fiske said yesterday that Guiffre, along with four other Northern Virginia alcohol distributors, United Beverage Co. of Alexandria, Northern Virginia Beverage Co. of Springfied, Virginia Imports Ltd. of Alexandria, and King Wholesaler Inc. of Chantilly, filed the suit to "clarify" the question of whether or not wholesalers will be subject to possible prosecution for entertaining prior to the enactment of the new state law.