CAH Designation Waiver Authority Act of 2009 - Amends title XVIII (Medicare) of the Social Security Act with respect to the Medicare rural hospital flexibility program a state may establish.
Authorizes state designation of a Medicare critical access hospital (CAH), even if it does not comply with the requirement that it be located more than a 35-mile drive from another hospital, if it is certified by the state on or after enactment of this Act as being a necessary provider of health care services to residents in the area. (Thus restores state authority that existed before January 1, 2006, to waive the 35-mile rule.)