When a deft faces criminal or civil penalties, deference to an agency's interpretations of its own regulations is inapposite, as an agency has an obligation to clearly state the rule.
http://media.ca11.uscourts.gov/opinions/pub/files/201710397.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.