U.S. Standards for Grades of Butter: https://www.ams.usda.gov/sites/default/files/media/Butter_Standard%5B1%5D.pdf
7 CFR Part 58.347 - Defines Butteroil and AMF https://www.law.cornell.edu/cfr/text/7/58.347
21 U.S. Code 321a - Butter defined https://www.law.cornell.edu/uscode/text/21/321a
21 CFR Part 101.4 - Ingredient names for butter products https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.4
21 CFR Part 101.67 - Nutrient Content Claims for butter products https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=101.67
Cream https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=131&showFR=1