From the article:
Facebook can legally be compelled by subpoena to provide basic account
information. However, federal law prohibits the social media giant from
disclosing user content (messages, timeline postings, photos) in
response to a civil subpoena. Depending on privacy settings, content may be visible only to friends or
to the public. With no fault divorces available in all 50 states and
D.C., the value of online evidence of infidelity is minimal.