A Virginia assistant attorney general argued in court in Alexandria yesterday that the three Northern Virginia beer distributors who filed suit against the state alcohol regulatory commission did so to ward off an investigation into their business entertainment practices.

Assistant Attorney General Donald A. Lahy said the beer distributors, who include an appointee of Gov. Charles S. Robb, initiated the civil suit because "they fear an adverse ruling" from the Virginia Alcohol Beverage Commission.

In the suit, filed in Alexandria Circuit Court, the beer distributors are challenging a state law that bans them from entertaining their retail customers. They are arguing that the law, which the 1985 General Assembly modified this spring, can be interpreted as allowing for such things as taking a retailer to sporting events.

Joseph M. Guiffre, a Springfield Anheuser-Busch distributor and an appointed member of the Virginia Highway and Transporation Commission, has been under federal and state investigation for suspected violations of the entertainment rule, according to Guiffre's attorney, David G. Fiske.

Fiske said his clients -- the Guiffre Distributing Co. and two Alexandria wholesalers, United Beverage Co. and Virginia Imports Ltd. -- have had their businesses damaged already because liquor agents have "harassed" their customers. He said the distributors are concerned that even after the new law, which will permit "routine business entertainment," takes effect July 1, the clients could still be subject to criminal prosecution and possibly lose their licenses.

Circuit Court Judge Donald H. Kent took the case under advisement and said he will rule within 30 days.