本文是介绍美国联邦制如何运作的三篇系列文章之一。另外两篇文章分别介绍地方政府和州政府。

美国的联邦法律适用于全国各地的每一个州和市。国会（Congress）和总统为制定和执行法律发挥了重要作用，但联邦政府还有其他分支和部门。

美国立法交流理事会（American Legislative Exchange Council）负责国际关系和联邦主义事务的主任卡拉∙琼斯（Karla Jones）在谈到执行国家外交和国防政策的联邦职能机构时候表示，“我们的确需要有国务院（State Department）。我们的确需要有国防部（Department of Defense）。

美国采取所谓“联邦主义”的体制，权力分别由地方、州和国家掌管。这是一个必须了解的重要观念，因为普通公民日常需要与不同级别的政府打交道，但方式并不相同。

联邦政府从事哪些工作?

只有联邦政府才能处理州际关系和对外商务，负责对外宣战和制定税务、开支等国家政策。

上述行动往往从国会立法开始。国会分众议院（House of Representatives）和参议院（Senate）。众议院有435名成员，参议院有100名成员。美国50个州不论人口多寡，每一个州可选出两名联邦参议员。各州的联邦众议员人数由各州人口决定。国会通过议案后，需经总统签字才能成为法律 。总统也可以对议案表示否决。

联邦行政分支由总统及其顾问和联邦各部、各机构组成，负责执行国会通过的法律。联邦各部由总统任命部长级官员，但需参议院确认。美国联邦政府设有十多个部门，各自承担特定的职责。例如财政部（Treasury Department）的职责包括货币的印制和监管。

总统还是美国武装部队的统帅，可以决定军事武器的使用、军队的部署和舰船的派遣等。军队将领都服从总统的指挥。

美国各级政府及分支机构的职能见以下图表。

最高法院（Supreme Court）是美国最高级别的联邦法院，负责保障美国人民在法律面前人人平等。最高法院由9名成员组成，其中一名是首席大法官，另有8名大法官。如果出现人们对国会通过的法律的合法性产生不同意见，或者对某联邦机构执行的监管有分歧等情况，最高法院负责公平和公正地解释法律。

美国宪法（Constitution）授权通过全国选举产生的总统提名最高法院大法官人选，但须经参议院确认，从而保证政府各分支的制衡 。

4月，特朗普总统（President Trump）提名的最高法院大法官尼尔·戈萨奇（Neil Gorsuch）宣誓就职。当时特朗普总统发表讲话表示，“国家缔造者采取分权的方式，是因为他们认识到这是保护我国公民和维护我国宪法尊严的最佳途径。”

最高法院的重大裁决往往对美国生活产生深远的影响，有些甚至延续到今天。例如，最高法院对1954年布朗诉教育局（Brown v. Board of Education）一案裁定公立学校的种族隔离为非法。

在总统向国会参众两院联席会议发表国情咨文（State of the Union）的时候， 联邦政府的三个分支都聚集在美国国会大厦（U.S. Capitol）聆听总统发表的报告。总统通过发表国情咨文推出下一年度的大政方针，一般每年1月或2月在新一届国会开幕后进行。特朗普总统预定在2018年1月30日发表上任后的第一份国情咨文。

本文由自由撰稿人Lenore T. Adkins撰写。

This article is part of a three-part series on how federalism works in America. Other installments focus on local and state governments.

Federal laws in America apply across the country in every state and city. Congress and the president have important roles to play in making and enforcing those laws, but they are not alone.

“We do need a State Department. We do need a Department of Defense,” says Karla Jones, director of international relations and federalism at the American Legislative Exchange Council, referring to the federal entities responsible for implementing the country’s foreign and defense policies.

The U.S. relies on a system called “federalism,” in which government powers are divided among local, state and national responsibilities. It’s an important concept to understand because citizens encounter different levels of government daily, but in several ways.

What does the federal government do?

Only the federal government can regulate interstate and foreign commerce, declare war and set taxing, spending and other national policies.

These actions often start with legislation from Congress, made up of the 435-member House of Representatives and the 100-member U.S. Senate. Each of the 50 states receives two senators regardless of its population size. The number of representatives each state receives depends on the state’s population. Bills that Congress approves then go to the president to sign into law or reject with a veto.

The executive branch is responsible for enforcing the laws Congress makes. It is made up of the president and his or her advisers, as well as multiple departments and agencies. The departments are each headed by a secretary, whom the president appoints with the advice and consent of the Senate. The U.S. has more than a dozen departments, and they each take on a specific set of duties. The Treasury Department’s duties, for example, include printing and regulating money.

The president also serves as commander­-in-­chief of the United States Armed Forces. That means the president directs how military weapons will be used, where to deploy troops and where ships are sent. The military’s generals and admirals take their direction from the president.

This graphic summarizes the kinds of entities in each branch of government.

The Supreme Court is the highest federal court in the U.S. and assures the American people of equal justice under law. The court’s nine justices — one chief judge and eight associate judges — interpret the law, in a fair and impartial manner, when disagreements arise on the legality of a law that Congress approves, a regulation that a federal agency implements or other matters.

The Constitution empowers the president, who is elected by the entire nation, to nominate justices. These justices require Senate confirmation to uphold the checks and balances among the branches of government.

“The Founders separated power because they knew it was the best way to protect our citizens and keep our Constitution secure,” President Trump said at the April swearing-in of Justice Neil Gorsuch, whom the president nominated to the Supreme Court.

Landmark decisions from the Supreme Court shape American life, and their ramifications are still felt today. They include the 1954 Brown v. Board of Education case, which outlawed racial segregation in public schools.

The three branches of the federal government get together at the U.S. Capitol when the president delivers the State of the Union address to a joint session of Congress. That speech represents an opportunity for the president to lay out an agenda for the coming year. These addresses are traditionally held in January or February after the new session of Congress convenes. President Trump’s first State of the Union address is scheduled for January 30, 2018.

This article was written by freelance writer Lenore T. Adkins.