A Delaware court has refused to disqualify a law firm that Air Products is using in its $5.1 billion bid to acquire rival Airgas. Air Products is using the services of Cravath, Swaine & Moore LLP, a law firm that has done work in the past for Airgas. Airgas sued, citing a conflict of interest.

Airgas has rejected Air Products' takeover offer.

According to Reuters, Cravath has worked consistently for Air Products for at least 43 years. It also worked for Airgas from May 2001 until October 2009, when it decided it could no longer work for Airgas in light of Air Products' brewing offer.

Delaware Chancellor William Chandler III said he had seen no evidence Cravath would use any information from its time representing Airgas in the buyout case.

Airgas said it was "disappointed" and still says that Air Product's offer "grossly undervalues" the company.

"We are prepared to take all necessary steps to preserve and protect stockholder value," Airgas said.