This paper reviews GPS investigations in Japan and the United States. In 2017, the Japanese Supreme Court held that warrantless GPS search was illegal. The case reviewed in this article illustrates the boundary of permissible investigation using advanced technology and highlights the fact that rapidly developing technology challenges legal research. In the 2017 decision discussed in this paper, law enforcement challenged the permissible scope of investigating warrantless GPS searches; a challenge common in other countries, like the U.S. The U.S. Supreme Court has already decided this case in United States v. Jones decision in 2012. Both of Japanese and American decision takes similar reasoning for their decisions.