The Administrative Procedures Act provides for both formal and informal rulemaking. Agencies, however, tend to prefer informal rulemaking because of the excesses of procedure provided for and hearing rights granted by the formal rulemaking process. My Administrative Law casebook provides an example:
[A]n FDA formal rulemaking to determine the percentage of peanuts a substance must contain in order to be labeled 'peanut butter' took nine years and twenty weeks of hearings producing 8,000 pages of hearing record, to produce a six-page opinion to justify a decision to require at least 90% peanuts.
Needless to say, the prospect of spending nine-and-a-half years on the Peanut Butter Standards Subcommittee has led FDA officials to prefer somewhat less formal rulemaking processes.