No. There is no grandfather clause in the ADA law. The legal standard – albeit vague – is if altering the violation is “readily achievable.” For example, my law school’s building was very old and had four floors, but the elevator only went up the first 3 floors, but not the 4th floor. In this case, it would probably not be readily achievable to make an alteration which would cause the elevator to go to the 4th floor because that would require a costly teardown of the entire building. On the other hand, if a wheelchair is unable to go into a business somewhere in the City of Julian because of a cement access barrier, the store owner could simply put up a sign with a bell that says “Please ask or ring for assistance”. This alteration would probably be considered a readily achievable fix.