Q. How should specific amendments to laws be cited? For example, if someone wanted to reference just the amended section and not the law in its entirety, how would the 1974 FECA amendments or the 2002 BCRA be cited in contrast to the original 1971 act?
A. According to CMOS 14.183, on laws and statutes,
Federal bills or joint resolutions that have been signed into law—“public laws,” or statutes—are first published separately, as slip laws, and then collected in the annual bound volumes of the United States Statutes at Large (abbreviated in legal style as “Stat.”), where they are referred to as session laws. Later they are incorporated into the United States Code (U.S.C.).
Adapting the suggested citation formats in CMOS, the original 1971 campaign finance law you’re alluding to (enacted in 1972) would be cited as follows (where the slip law is cited ahead of the session law):
Federal Election Campaign Act of 1971, Pub. L. No. 92-225, 86 Stat. 3 (1972).
The 1974 amendments would be cited in the same way (regardless of whether you’ve cited the 1971 act), as would the amendments in the Bipartisan Campaign Reform Act of 2002:
Federal Election Campaign Act Amendments of 1974, Pub. L. No. 93-443, 88 Stat. 1263.
Bipartisan Campaign Reform Act of 2002, Pub. L. No. 107-155, 116 Stat. 81.
The 1971 law and subsequent amendments can be cited collectively in the United States Code like this:
Federal Election Campaign Act of 1971, as amended, 52 U.S.C. §§ 30101–30146.
In case you’re wondering how we got that info, we used Google to find the relevant documents at US government websites. A search for “FECA 1974” led us to the 1974 amendments at Congress.gov, including a scan of the amendments in the Statutes at Large. That’s where we found the title “Federal Election Campaign Act Amendments of 1974” (toward the top of the first page) as well as “Public Law 93-443” (abbreviated in our citation). The form “88 Stat. 1263” can be found there also (“1263” is the first page in vol. 88 of the Statutes at Large). A separate search for “BCRA 2002” likewise brought up the relevant text. We located the 1971 act in title 52 of the current US Code (at House.gov) in a similar manner.
Most of Chicago’s advice for citing legal documents (starting at CMOS 14.170) relies on The Bluebook: A Uniform System of Citation, published by the Harvard Law Review Association. Information not found in CMOS can usually be found there.