The Obama administration’s Justice Department argued this week that a Senate Democrat is demonstrating a “fundamental misunderstanding of the law” by pushing to declassify a 13-year-old guidance document on surveillance.

The dispute involves a 2003 memorandum issued by the Justice Department’s Office of Legal Counsel pertaining to surveillance and “commercial service agreements.” The Justice Department defended its decision to keep the memo secret after Sen. Ron Wyden, D-Ore., filed a brief in support of a lawsuit seeking to make the document public.