The Washington Capitals received a double-dip portion of good news yesterday. First, defenseman Pierre Bouchard agreed to a two-year contract. Then NHL President John Ziegler awarded the Capitals Swedish winger Begt-Ake Gustafsson, whom he had assigned to Edmonton in a controversial ruling in June.

Gustafsson was drafted by Washington in June 1978, but he remained in Sweden last winter. Edmonton, then a member of the World Hockey Association, contacted Gustafsson in September and made several offers, finally signing him in March.

Meanwhile, the NHL and WHA agreed on a merger and among the clauses was one that specified that none of thefour WHA teams entering the NHL could add players after Jan. 1, 1979.

Peter O'Malley, principal architect of the merger agreement, felt this locked up Gustafsson. Ziegler, however, first ruled that the initial offer and continuing negotiations were evidence of good-faith bargaining and gave his rights to Edmonton, which made Gustafsson one of its two protected players.

The Capitals appealed and produced evidence that Edmonton had set a deadline on negotiations, besides using the prospective merger as a device to sign Gustafsson, who had expressed a desire to play in the NHL.

On the basis of the new evidence that was presented in Toronto Wednesday, Ziegler yesterday reversed himself and assigned Gustafsson to the Capitals, who said they would accept the contract terms Gustafsson had made with Edmonton.

"The night we met with the WHA I read the sentence on player acquisition to (Edmonton owner Peter) Pocklington and asked if he understood that this ruling pertained to Gustafsson," O'Malley said last night. "He said he did. Everything that followed was a highhanded attempt to circumvent the rules."

Edmonton is unlikely to appeal the latest ruling to the NHL Board of Governors, O'Malley said, because the Oilers presented a memorandum at Wednesday's hearing to the effect that they considered Ziegler to be "the final, binding authority."

Although the popular Bouchard earlier expressed displeasure with his drawn-out salary negotiations, he said he was pleased with the way things went during yesterday's session with O'Malley that produced the signed contract.

Bourchard, 31, played only one game last season, the Capitals' finale on April 8. He announced his retirement after the Capitals took him from Montreal in the preseason intraleague draft, then decided that he wanted to return to hockey.

Defensemen Peter Scamurra has agreed to terms of a new contract, following his victory in the Buffalo men's doubles tennis tournament. But defensemen Rick Green and Gord Lane still are far from contract settlement and seem destined to play out their options this season.