Codification — the process of pulling together a body of law into one convenient place — is one of the classic hard problems of access to the law. It never seems hard when one sets out; back in Merrie Olde 12th century England, Parliament’s practice was to take new laws, copy out a handful of copies by hand, circulate those copies to various local officials, and call it a day. The problem that Statutes of the Realm was trying to deal with was that seven centuries later, this sequential process had produced such a vast body of accumulated laws that merely compiling the index took four years.

In the 1930s in the U.S., the alphabet soup of newly created New Deal agencies produced a similar mess. One infamous 1935 case, Panama Refining Co. v. Ryan (colloquially known as the “Hot Oil case,” because it dealt with illegal interstate shipments of petroleum), reached the Supreme Court before anyone realized that one of the laws the government was trying to enforce against the oil companies wasn’t in force at the relevant time. It had been repealed (by mistake, it turned out) over a year before, without anyone noticing. People had been threatened with criminal punishment for violating a “law” that wasn’t. The outcry—at least among law professors—led to the establishment of the Federal Register, a chronological log of all the regulatory actions taken by federal agencies, and the Code of Federal Regulations, which captures a current snapshot of the regulations currently in force.

There are various codification strategies out there, with advantages and drawbacks that would take us too far afield to discuss in much detail. One strategy is for someone with a lot of time to pore through the last N years of statutes, pull out the ones that are still relevant, and compile them into a single, authoritative text. The legislature then repasses the authoritative version, and repeals everything else. Another is for someone simply to compile the reams and reams of statutes into a logical arrangement that then becomes evidence of what the law says; if you really want to get it right, you need to go back and check the original act as it was passed. Governments in the U.S. use a mixture of both of these processes. Once you have a compilation of this sort, it becomes much easier for the legislature to make changes in place. They can say “we’re repealing this section and replacing it with this new text,” which keeps things from getting as messy as quickly. (Think of the list of statutes as a blog, and the codified version as a wiki.)

(This article is licensed. It is canonically available and has been written by James Grimmelmann with inputs from others.)