After the terrorist attacks of September 11, 2001, the Homeland Security Act was enacted in 2002 by U.S. Congress. It includes in a provision, the Critical Infrastructure Information Act (CIIA), which may give much affect on current laws such as the Freedom of Information Act (FOIA). CIIA allows the Department of Homeland Security to withhold critical infrastructure information that is voluntarily submitted to it by private entities regarding the security of critical infrastructure and protected systems. This article focuses on CIIA's advantages and disadvantages and analyzes their provisions and scholastic argument of CIIA and CIIA's final rule. Chapter 2,3 and 4 includes a summary of CIIA and CIIA's final rule. Chapter 5 and 6 take up the scholastic argument for or against CIIA. JW. Conrad demonstrates that national security can be served under existing law such as the CIIA. On the other hand, CE. Wells insists that Congress should amend FOIA and CIIA to counteract the government's tendency toward excessive secrecy. Chapter 7 describes that CIIA and scholarship of CIIA are significant for Japanese information legal systems, because it is possible that terrorist attacks might arise in Japan.