N.Y. MHY. LAW § 81.29 : NY Code - Section 81.29: Effect of the appointment on the incapacitated person

(a)  An  incapacitated  person  for whom a guardian has been appointed
  retains all powers and rights except those powers and rights  which  the
  guardian is granted.
    (b)  Subject  to subdivision (a) of this section, the appointment of a
  guardian shall not be conclusive evidence that the person lacks capacity
  for any other purpose, including the capacity to dispose of property  by
  will.
    (c)  The title to all property of the incapacitated person shall be in
  such person and not in the guardian. The property shall  be  subject  to
  the  possession  of the guardian and to the control of the court for the
  purposes of administration, sale or other disposition only to the extent
  directed by the court order appointing the guardian.
    (d) If the court determines  that  the  person  is  incapacitated  and
  appoints  a  guardian,  the  court  may  modify,  amend,  or  revoke any
  previously executed appointment,  power,  or  delegation  under  section
  5-1501,  5-1505, or 5-1506 of the general obligations law or section two
  thousand nine hundred sixty-five of the public health  law,  or  section
  two   thousand   nine  hundred  eighty-one  of  the  public  health  law
  notwithstanding section two thousand  nine  hundred  ninety-two  of  the
  public  health  law,  or any contract, conveyance, or disposition during
  lifetime or to take effect upon death, made by the incapacitated  person
  prior  to  the  appointment  of the guardian if the court finds that the
  previously   executed   appointment,   power,   delegation,    contract,
  conveyance, or disposition during lifetime or to take effect upon death,
  was  made  while the person was incapacitated or if the court determines
  that there has been  a  breach  of  fiduciary  duty  by  the  previously
  appointed  agent.  In such event, the court shall require that the agent
  account to the guardian. The court shall  not,  however,  invalidate  or
  revoke  a  will  or  a  codicil  of  an  incapacitated person during the
  lifetime of such person.
    (e) Nothing in this article shall be construed either  to  prohibit  a
  court from granting, or to authorize a court to grant, to any person the
  power  to  give  consent  for  the  withholding  or  withdrawal  of life
  sustaining treatment, including artificial nutrition and hydration. When
  used in this article, life sustaining treatment means medical  treatment
  which  is  sustaining  life  functions  and  without which, according to
  reasonable medical judgment, that patient will die within  a  relatively
  short time period.