2014 New York Laws
EPT - Estates, Powers & Trusts
Article 10 - POWERS
Part 6 - (10-6.1 - 10-6.9) RULES GOVERNING EXERCISE OF A POWER OF APPOINTMENT
10-6.7 - Exercise by all donees; exceptions

10-6.7 Exercise by all donees; exceptions
Whenever  a  power  of appointment, other than a power in a trustee to
  invade trust principal under section 10-6.6 of this article or under the
  terms of the dispositive instrument, is created in two or  more  donees,
  all  must  unite  in  its  exercise, unless the instrument creating such
  power provides otherwise. But, if before its execution, one or  more  of
  such  donees dies or becomes incompetent, such power may be exercised by
  the survivor or the competent donee, unless such exercise is  explicitly
  barred by the terms of the instrument creating such power.