As noting in a newly published request for information on prescription drug software (83FR58574), FDA has a regulation which lays out its own rules for issuing these guidance documents. See 21 CFR 10.115.
FDA has two types of Guidance Documents, Level 1 or Level 2. Level 1 sets out FDA interpretation of statute, regulation, or has complex scientific content. Any other guidance document is "Level 2."
The regulation was established by 64 FR 56477, 13pp, 9/19/2000, with a trivial amendment regarding a web link in 2018, 83 FR 13416, 3/29/2018.
|Sec. 10.115 Good guidance practices.|