Walgreen Co. has sued Crowell & Moring in a Washington court over claims the law firm refused to surrender a decade-old client file to a legal team at a different firm.

Attorney ethics rules and regulations control the possession and transfer of client files, and the Walgreens suit pointed to District of Columbia provisions. The previously unreported suit sought emails, memos, billing invoices, notes, time-keeping records and other items related to work Crowell did in 2008 on a new prescription drug initiative tied to Walgreens.