Title III also has applications to existing facilities. One of the definitions of "discrimination" under Title III of the ADA is a "failure to remove" architectural barriers in existing facilities. See 42 U.S.C. § 12182(b)(2)(A)(iv). This means that even facilities that have not been modified or altered in any way after the ADA was passed still have obligations. The standard is whether "removing barriers" (typically defined as bringing a condition into compliance with the ADAAG) is "readily achievable", defined as "...easily accomplished without much difficulty or expense".

The World Wide Web Consortium (W3C) established the main international standards and accessibility for the World Wide Web. The WCAG is created by the W3C to provide a standard for web content accessibility that can be shared around the world. The WCAG is meant to accompany organizations as a sort of blueprint on how to make their websites ADA compliant.
Spector v. Norwegian Cruise Line Ltd.[64] was a case that was decided by the United States Supreme Court in 2005. The defendant argued that as a vessel flying the flag of a foreign nation it was exempt from the requirements of the ADA. This argument was accepted by a federal court in Florida and, subsequently, the Fifth Circuit Court of Appeals. However, the U.S. Supreme Court reversed the ruling of the lower courts on the basis that Norwegian Cruise Lines was a business headquartered in the United States whose clients were predominantly Americans and, more importantly, operated out of port facilities throughout the United States.