Must the USCIS abide by the Code of Federal Regulations (CFR), or is the CFR just a set of guidelines that aren't legally binding?

Question

I wonder whether the United States Citizenship and Immigration Services (USCIS) must abide by the Code of Federal Regulations (CFR) or the CFR is just a set of guidelines that aren't legally binding (i.e., the USCIS may take actions/decisions that contradict the CFR without potentially facing legal consequences).

I'm mostly interested in the part of the CFR that pertains to the naturalization process, if that matters, e.g. 8 CFR 316.5(b)(5)(ii):

(ii) Return to the United States. If, upon returning to the United States, an applicant returns to the State or Service district where the applicant last resided, the applicant will have complied with the continuous residence requirement specified in § 316.2(a)(5) when at least three months have elapsed, including any part of the applicant's absence, from the date on which the applicant first established that residence. If the applicant establishes residence in a State or Service district other than the one in which he or she last resided, the applicant must complete three months at that new residence to be eligible for naturalization.

The naturalization applications are handled by the USCIS.

Since I read on https://www.uscis.gov/policy-manual:

The [USCIS] Policy Manual contains the official policies of USCIS and assists immigration officers in rendering decisions. The Policy Manual is to be followed by all USCIS officers in the performance of their duties but it does not remove their discretion in making adjudicatory decisions. The Policy Manual does not create any substantive or procedural right or benefit that is legally enforceable by any party against the United States or its agencies or officers or any other person.

I wonder if, unlike the USCIS Policy Manual, the CFRs are legally enforceable.

Answer 1

Much of the Code of Federal Regulations consists of restatements of statutory provisions found in the United States Code. In the case of Title 8, CFR, these provisions are largely to be found in Title 8, USC, which codifies the Immigration and Nationality Act. To the extent that anything in the CFR duplicates a statute, it's legally binding, because it is in fact a statutory provision.

That case is not particularly interesting to your question, of course. There is another law that governs the CFR, which is the Administrative Procedure Act. In short, this law requires the executive to abide by its promulgated regulations and not to change them without following certain procedures, and it gives the courts the power to enforce this.

Therefore, the answer to the question

Must the USCIS abide by the Code of Federal Regulations (CFR)?

Is basically yes. If you believe they haven't, you can take them to court.