28 CFR Part 36 Nondiscrimination on the Basis of Disability by Public Accommodations and in Commercial Facilities NPRM (2008 Title III NPRM)

(3) A public accommodation shall not rely on an individual accompanying an individual with a disability to interpret or facilitate communication, except in an emergency involving a threat to public safety or welfare, or unless the individual with a disability specifically requests it, the accompanying individual agrees to provide the assistance, and reliance on that individual for this assistance is appropriate under the circumstances.