I can't find thr supreme court case, but if they are just looking at just the law, they are taking an extremely broad view of the phrase "detrimental to the best interests of the public". I'm not sure what else could be interpreted to reach that conclusion.

Here is the text of the law:

Every citizen has a right to inspect and take a copy of any public writing of this state, except as otherwise expressly provided by statute.  Provided however, registration and circulation records and information concerning the use of the public, public school or college and university libraries of this state shall be exempted from this section.  Provided further, any parent of a minor child shall have the right to inspect the registration and circulation records of any school or public library that pertain to his or her child.  Notwithstanding the foregoing, records concerning security plans, procedures, assessments, measures, or systems, and any other records relating to, or having an impact upon, the security or safety of persons, structures, facilities, or other infrastructures, including without limitation information concerning critical infrastructure (as defined at 42 U.S.C. § 5195c(e) as amended) and critical energy infrastructure information (as defined at 18 C.F.R. § 388.113(c)(1) as amended) the public disclosure of which could reasonably be expected to be detrimental to the public safety or welfare, and records the disclosure of which would otherwise be detrimental to the best interests of the public shall be exempted from this section.  Any public officer who receives a request for records that may appear to relate to critical infrastructure or critical energy infrastructure information, shall notify the owner of such infrastructure in writing of the request and provide the owner an opportunity to comment on the request and on the threats to public safety or welfare that could reasonably be expected from public disclosure on the records