Unfortunately the release is authorized by law. It is called the freedom of information act, and it requires that all information is releasable unless it fits into a specific FOIA exemptions (national security info, personal info, law enforcement info, etc.). If it isn't specifically exempt under that statute it is not only releasable, but it must be released upon request. A government operating manual is certainly releasable, and whichever public official marked this document as exempt could be prosecuted to the full extent of the law (ha! like that is going to happen).
Yep, and the burden is on the government to prove why documents like these should be considered exempt (which they’re not).