Japan court rejects AI inventorship in DABUS patent fight

Japan’s Supreme Court dismissed the final appeal in the country’s DABUS litigation on March 4, 2026, confirming that AI systems cannot be named as patent inventors under Japanese law. The case stemmed from a Patent Cooperation Treaty application filed in September 2019 by researcher Stephen Thaler for a food container and devices for attracting enhanced attention, with DABUS listed as the inventor.

Japanese courts found that the Patent Act assumes an inventor is a natural person capable of holding legal rights. They also rejected Thaler’s claim that ownership of DABUS entitled him to its output, finding that AI is not a tangible object that can be owned in the relevant legal sense.

The ruling aligns Japan with decisions in the US, UK, EU, Germany, Australia, and Canada, where courts and patent offices have rejected AI as a legal inventor. South Africa accepted a DABUS patent, but the report describes that outcome as a procedural artifact because its system does not conduct substantive examination at the application stage.

The unresolved issue is how much human input is enough when AI assists in research. USPTO guidance that took effect on November 28, 2025 treats AI tools as comparable to lab equipment or software, applying the same conception test that requires a human to form a definite and permanent idea of the complete invention.