The GPO's recent electronic publication of all legislation enacted by Congress from 1951-2009 is noteworthy for several reasons. It makes available nearly 40 years of lawmaking that wasn't previously available online from any official source, narrowing part of a much larger information gap. It meets one of three long-standing directives from Congress's Joint Committee on Printing regarding public access to important legislative information. And it has published the information in a way that provides a platform for third-party providers to cleverly make use of the information. While more work is still needed to make important legislative information available to the public, this online release is a useful step in the right direction.
Narrowing the Gap
In mid-January 2013, GPO published approximately 32,000 individual documents, along with descriptive metadata, including all bills enacted into law, joint concurrent resolutions that passed both chambers of Congress, and presidential proclamations from 1951-2009. The documents have traditionally been published in print in volumes known as the "Statutes at Large," which commonly contain all the materials issued during a calendar year.
The Statutes at Large are literally an official source for federal laws and concurrent resolutions passed by Congress. The Statutes at Large are compilations of "slip laws," bills enacted by both chambers of Congress and signed by the President. By contrast, while many people look to the US Code to find the law, many sections of the Code in actuality are not the "official" law. A special office within the House of Representatives reorganizes the contents of the slip laws thematically into the 50 titles that make up the US Code, but unless that reorganized document (the US Code) is itself passed by Congress and signed into law by the President, it remains an incredibly helpful but ultimately unofficial source for US law. (Only half of the titles of the US Code have been enacted by Congress, and thus have become law themselves.) Moreover, if you want to see the intact text of the legislation as originally passed by Congress -- before it's broken up and scattered throughout the US Code -- the place to look is the Statutes at Large.
In 2011, GPO published 58 volumes of the Statutes at Large, covering 1951-2009, but did not break the volumes down into their constituent documents. Up until that point, the public laws were available as individual documents on THOMAS from 1989 to present as HTML (and PDF in some instances), and from 1789 to 1875 as TIFF (unwieldy image) files from the Library of Congress. Even with this recent release, 76 years of federal law are still unavailable online in any format from any official source; and the files released for the years 1789 to 1875 by the Library of Congress are difficult to use.