37 C.F.R. § 42.57

(a) Privileged communications. A communication between a client and a USPTO patent practitioner or a foreign jurisdiction patent practitioner that is reasonably necessary and incident to the scope of the practitioner's authority shall receive the same protections of privilege under Federal law as if that communication were between a client and an attorney authorized to practice in the United States, including all limitations and exceptions.

(b) Definitions. The term “USPTO patent practitioner” means a person who has fulfilled the requirements to practice patent matters before the United States Patent and Trademark Office under § 11.7 of this chapter. “Foreign jurisdiction patent practitioner” means a person who is authorized to provide legal advice on patent matters in a foreign jurisdiction, provided that the jurisdiction establishes professional qualifications and the practitioner satisfies them. For foreign jurisdiction practitioners, this rule applies regardless of whether that jurisdiction provides privilege or an equivalent under its laws.

(c) Scope of coverage. USPTO patent practitioners and foreign jurisdiction patent practitioners shall receive the same treatment as attorneys on all issues affecting privilege or waiver, such as communications with employees or assistants of the practitioner and communications between multiple practitioners.