14 CFR 300.6: Practitioners' standards of conduct.

Every person representing a client in matters before DOT in all contacts with DOT employees, should:

(a) Strictly observe the standards of professional conduct;

(b) Refrain from statements or other actions designed to mislead DOT or to cause unwarranted delay;

(c) Avoid offensive or intemperate behavior;

(d) Advise all clients to avoid improprieties and to obey the law as the attorney believes it to be; and

(e) Terminate the professional relationship with any client who persists in improprieties in proceedings before DOT.