U.S. stock exchange rules are usually posted free on the relevant exchange's web site (e.g., NASDAQ, CSX, NSX, Direct Edge, BATS, and the NYSE Listed Company Manual).
Stock exchange rules can also be found in the CCH "Guide" (ex., the New York Stock Exchange Guide) or "Manual" (e.g., the NASDAQ Manual) for that exchange, which are available as looseleafs or on CCH's subscription-based Intelliconnect. Also, the exchange may sell a print version of its rules.
For better searching, the NYSE Rules are available on Lexis (FEDSEC;NYSECR) and Westlaw (NYSE-RULES).
Comment Letters: Letters sent by the public to express their opinions on proposed rules are called "comment letters." Comment letters sent to U.S. securities-related Self-Regulating Organizations (SROs) -- such as FINRA and, formerly, the NYSE and NASD -- are available through LIVEDGAR.
Foreign Exchanges: Most foreign stock exchange rules are published in a multi-volume looseleaf called International Securities Regulation: Stock Exchanges of the World, published by Oceana. Foreign stock exchange rules may also be found on the exchanges' Web site; check the sites listed in "Stock Exchanges" entry, or search for the site with a good search engine.
If that doesn't work, some foreign exchanges have offices in the U.S., especially New York City, and they may provide rules. For example, the Listing Manual for Foreign Companies for the Tokyo Stock Exchange has been available from the New York office of the TSE (212-363-2350). If all else fails, try to contact the Exchange in its home country. If even that fails, post a request on Law-Lib.