。
Japan employs a first-to-file system.
Literal
Japan [topic-は] first-to-file principle [object-を] adopting.
先願主義 (せんがんしゅぎ, 'first-to-file principle') is patent law vocabulary: the first person to file a patent application gets the rights, regardless of who invented first. 採用している ('is employing/adopting') is the standard verb for systems and policies. A concise legal/technical sentence about intellectual property law.