• It is an anonymous work or pseudonymous work and 25 years have passed since the year of its publication
• It is a sound recording and 50 years have passed since the date of its creation
• It is a photographic work or film and 25 years have passed since the year of its publication
• It is literary, musical or artistic work other than photograph and 25 years have passed since the year of death of the author (or last-surviving author)
• It is a government work and 25 years have passed since the year of its publication

Per U.S. Circ. 38a., the following countries are not a participant in the Berne Convention or any other treaty on copyright with the United States:

• Afghanistan, Eritrea, Ethiopia, Iran, Iraq, Kiribati, Nauru, Palau, San Marino, São Tomé and Príncipe, the Seychelles, Somalia, Turkmenistan and Tuvalu.

As such, works published by citizens of these countries in these countries are usually not subject to copyright protection outside of these countries. Hence, such works may be in the public domain in most other countries worldwide.

However

• Works published in these countries by citizens or permanent residents of other countries that are signatories to the Berne Convention or any other treaty on copyright will still be protected in their home country and internationally as well as locally by local copyright law.
• Similarly, works published outside of these countries within 30 days of publication within these countries will also usually be subject to protection in the foreign country of publication. When works are subject to copyright outside of these countries, the term of such copyright protection may exceed the term of copyright inside them.
• Unpublished works from these countries may be fully copyrighted.