The spectrum is managed by a number of different organizations. The most visible to the general public is the Federal Communications Commission (FCC). The FCC manages civilian, state, and local government usage of the radio spectrum. This is the regulatory organization that affects you.
The FCC has a set of rules and regulations that define use of spectrum, as well as policies and procedures for working with the FCC. You can obtain these in hardcopy by ordering the Code of Federal Regulations, Title 47 from the Government Printing Office (GPO) at http://bookstore.gpo.gov/.
Companies such as Pike and Fischer (http://www.pf.com/) offer subscription services to the updated FCC regulations, policies, and proposed rules. There are also free (but slightly dated) versions of the FCC rules online. The "Hypertext FCC Rules Project" run by Harold Hallikainen at http://www.hallikainen.com/FccRules is one such project.
Harold's site actually indexes the GPO's online version of the rules. You can go directly to the GPO's online version of the rules at http://www.access.gpo.gov/nara/cfr/cfr-table-search.html.
The GPO's site points to all of the Code of Federal Regulations (CFR); you want the section labeled Title 47 - Telecommunication.
The FCC has the authority to investigate any user of the band. In fact, they can actually come onsite and inspect the operation of equipment:
15.29(a) Any equipment or device subject to the provisions of this part, together with any certificate, notice of registration or any technical data required to be kept on file by the operator, supplier or party responsible for compliance of the device shall be made available for inspection by a Commission representative upon reasonable request.
The FCC has very limited resources for enforcement?the trend for the last couple of decades has been toward deregulation and the reduction of staffing in the enforcement bureaus. The FCC will usually not visit you unless they receive a complaint. There have been rare reports of the FCC going after WISPs when they interfered with Part 97 (amateur radio) users. Working with the co-users of these bands is in your best interest, as they will be the ones complaining.
The National Telecommunications and Information Administration (NTIA) works with the Interdepartmental Radio Advisory Committee (IRAC), which manages federal use of the spectrum. You are not likely to hear from them unless you've done something really wrong.