军人以服从命令为天职，这是一句耳熟能详的话。那么，世界第一军事强国——美国的军队对此事如何规定的呢？
一、军人有服从命令的义务（Duty to Follow Orders）
美军军法条列（UCMJ——the Uniform Code of Military Justice）规定，军事人员必须服从命令：
1、服从法定上级军官所下的命令。〔890.ART.90（2））；
2、服从法定的准尉军官及士官的命令。〔890.ART.91（2）〕；
3、服从来自符合军规条例的命令〔890.ART.92（1）〕；
4、服从合法的命令。〔890.ART.92（2）〕。
二、军人有不服从非法命令的义务（Duty to Disobey Unlawful Orders）
军人有不服从非法命令的义务。You are not required to obey unlawful orders.
美军军人宣誓誓言：
Army officer appointment acceptance and oath of office I (insert name), having been appointed a (insert Rank) in the U.S. Army under the conditions indicated in this document, do accept such appointment and do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic, that I will bear true faith and allegiance to the same; and that I take this obligation freely, without any reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God. (DA Form 71, 1 August 1959, for office.)
Oath of Enlistment I, (NAME), do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; and that I will obey the orders of the President of the United States and the orders of the officers appointed over me, according to regulations and the Uniform Code of Military Justice. So help me God.
1、军人宣誓捍卫美国宪法，反抗国内和国外的敌人。宪法是根本大法，一切以宪法为准，凡不符合宪法的命令都是非法命令。
2、除宪法外还必须遵守日内瓦国际公约。该公约第三条规定得很清楚：“ 非敌对人员，放下武器的敌人，伤病员、俘虏，必须以人道待之，不分种族、性别、宗教信仰、年龄、财产等等。凡违背这些法律的命令都是非法的。
3、具体用什么方法来拒绝执行呢？
首先，要求上级的命令，以书面形式来表达，不祇是口头命令；
第二，如果已经是书面的命令，你要告诉上级，你打算拒绝执行命令；
最后，要求由军事法庭裁决。
这样，“军人以服从命令为天职”的原则从语境中看，“命令”一词毫无疑问指的是合法命令；而且更重要的是，军人如果执行了不合法的命令，本身还要承担罪责 ( "I was only following orders”has been unsuccessfully used as a legal defense of cases." ) 可见，军事人员不仅有拒绝执行命令的义务，而且从保护自己的角度出发，他们必须拒绝执行非法命令。如果他们执行了是要承担罪责的。
总之，军事人员有义务和责任执行上级下达的命令，同时也有义务和责任拒绝执行上级下达的非法命令。就算是总统下达的，祇要违背了宪法、军事法和国际公约，都可以而且必须拒绝。
