There are a few federal regulatory agencies that are involved in this area, including the FDA, USDA and the EPA. Each regulatory scheme is unique, but there are similar features. All of the agency's powers are set forth in the agency's enabling statute (power to issue regulations, investigate, prosecute, and/or adjudicate). Also the Administrative Procedure Act controls the administrative processes for all agencies.
Types of documents a researcher might be interested in include:
It is highly advisable for researchers to go to the agency's website. Much more information can be found here. Either look for a menu at the top of the site or go to the bottom of the site to find regulations, decisions, notices, letters or other legal materials.