Federal law comes from statutes, regulations, and court opinions. Much of this information is available for free online. If you need assistance navigating the resources below, try contacting one of the law libraries under the general Legal Information tab; the librarians there may be able to help you. You may also want to consult Pennsylvania Legal Research 101 as a guide to the legal system.
Once a federal law is passed by Congress, it is published as a public law (also known as a slip law) and assigned a public law number. For example, Public Law 115-7 was the seventh law that the U.S. Congress passed during its 115th legislative session. Public laws passed from 1995-present are collected at the U.S. government's govinfo.gov website.
At the end of each session of Congress, the slip laws are compiled into the Statutes at Large. The Statutes at Large is a chronological arrangement of the laws in order of enactment, so you can see all of the laws that Congress passed during each legislative session. Statutes at Large is available at govinfo.gov for the years 1951 - 2016.
As new laws are passed they are incorporated into the United States Code, which is a codification of federal statutory law arranged by subject. The U.S. Code is generally the best way to find the current state of federal statutory law because (unlike public laws or Statutes at Large) it is maintained and kept current over time as laws are passed, modified, and repealed.
Federal administrative law (legally binding rules made by administrative agencies such as the Department of Transportation and Department of Labor) is codified in the Code of Federal Regulations.
The Federal Register is the official daily publication for all final and proposed rules and regulations, notices of Federal agencies, and executive orders and other Presidential documents. It is published Monday-Friday, except on Federal holidays and is organized chronologically.
Structure of the Federal Courts
Federal Courts in Pennsylvania
In Pennsylvania, there are 3 federal district courts: Eastern (Philadelphia); Middle (Harrisburg & Scranton); and Western (Pittsburgh). These courts handle most of the day-to-day business of administering federal cases and trials. The Third Circuit Court of Appeals hears appeals from federal courts in Pennsylvania, Delaware, New Jersey, and the Virgin Islands.
Locating Federal Court Opinions
Federal Court documents, including court opinions, orders, motions, briefs, etc., are required to be filed electronically through PACER, which stands for "Public Access to Court Electronic Records." PACER is an electronic database that contains case and docket information from federal appellate, district and bankruptcy courts. Anyone can sign up for a PACER account for free, but there are fees associated with accessing the information and/or documents. Some (but not all) federal court filings can be found for free using a service called RECAP.
U.S. Supreme Court opinions are available from several sources:
Supreme Court website (1991-present)
Cornell, Legal Information Institute (1990-present)
Library of Congress (1754-2012).
You can search for decisions from all federal courts for free online using Google Scholar.