當國家面臨戰爭或恐怖攻擊等危機時，國家安全常成為政府採取緊急措施之理由，即使在和平時期國家安全亦常以各種不同理由，為法律、命令及司法院大法官解釋所援用，國家安全本身為不確定法律概念，即使無法明確定義，至少可以探求其射程範圍與決策程序，因為在民主法治國家，即使國家安全非常重要，也應該遵守法律保留原則，不容許成為一人決策或少數人決定之獨裁政治，所以國會監督程序就非常重要。本文首先討論國家安全定義、範圍與決定程序，其次以比較法觀點，就美國911 事件後以「國家安全」為名從事反恐戰爭，實施愛國者法、以軍事法庭審判美國公民等違反人權事項加以探討。

When a nation faces the threat of war, terrorist attacks or other similar crisis, “national security” is often used by governments as an excuse to justify for emergency legislation.Even in peaceful time, the term of “national security” can often be found in laws,regulations and judicial interpretation. Although national security has no fixed meaning by itself, we still can search for the range of this term and the decision-making process for national security purpose. In a democratic country, despite the importance of national security,government decisions are still subject to the principle of legal reservation. Such decisions
cannot be made by a single person or a small group of people. Therefore, the oversight of congress on government decisions is vital.Base on the above ideas, this paper deals with the definition, scope and decision-making processes of national security. Then, discussing how the United States uses “national security”as a tool in the so-called “war against terrorism” after 911 terrorist attacks from the view of comparative law perspective. The enforcement of the Patriot Act and the trial of American
citizens in military tribunals are also discussed.