Non-copyright restrictions

House rules: The owner of a property or facility may prohibit or restrict photography.
Trademark: Logotypes and other designs could be protected such that other parties may not use it for marketing and identification.
Personality rights: A person may or may not consent to a photograph being taken of them, let alone published under a free license.
Database rights: The effort and investment spent on compiling data into a database grants a property right.
Moral rights: An author has rights that protects them against derogatory action against their work, such as destruction and defacing.
Publication rights: After the original copyright of an unpublished work expires, publishing it may create a separate copyright.
Patents: Inventions and technologies, including but not limited file formats and design files, can be protected from reuse and distribution by their authors.
Insignia: Flags, coat of arms, seals, decorations, and similar symbols of authoritative entities are often restricted from being used by parties other than those symbolized.
Political symbolism: Certain political, ideological or social symbols are restricted from use in some countries.
Free speech exceptions: Many countries prohibit the expression of certain ideas, including hate speech, defamation, and encouraging violence.
Classified information: Many governments prohibit publication and distribution of material deemed important to state security.
Weapons manufacturing: Material that facilitates the creation of weapons, particularly models for 3D printing, are prohibited in many countries.
Pornography: Sexually explicit material often carries restrictions on publication and usage, such as whether or not minors may access it.
Pornography of minors: Sexual or erotic material featuring persons below a certain age are prohibited in most countries.
Content moderation: Websites and other content providers (including Wikimedia Commons) set rules on what information is and is not allowed.