capitalization of government bodies and offices
Full official names versus generic references.
Capitalize the full official name: the Department of Justice, the Senate, the Supreme Court. Lowercase the generic word when it stands alone: the department issued a memo, a senate in each state. Capitalize President, Queen, and like titles before a name: President Lincoln. Lowercase the title after a name or used alone: the president spoke.
Examples
Use the Department of State
Use The department issued a memo.
Avoid the Department issued a memo. (If you have not named it.)