WASHINGTON — The Association of Corporate Counsel and the U.S. Chamber of Commerce have joined an aerospace defense company in its court fight with the Internal Revenue Service in a closely watched tax case with work product protection at its core.

U.S. v. Textron, pending in the 1st U.S. Circuit Court of Appeals, concerns the enforcement of an IRS summons seeking production of Textron’s tax accrual work papers. A federal district court last August held that the Rhode Island-based company’s workpapers were protected by the work product protection and it refused to enforce the summons.