The Board’s guidelines are not mandatory on the public, but instead serve as the baseline for enforceable standards (which are) maintained by other Federal agencies.  In this respect, they are similar to a model building code in that they are not required to be followed except as adopted by an enforcing authority.  Under the ADA, the Department of Justice (and in the case of transit facilities, the Department of Transportation) are responsible for enforceable standards based on the Board’s guidelines.  These agencies will update their ADA standards based on the new guidelines.  In doing so, they will indicate when the new standards are to be followed.  Several other agencies (the General Services Administration, Department of Defense, Department of Housing and Urban Development, and the U.S. Postal Service) hold a similar responsibility for standards used to enforce the ABA.