ยง  5-308.  Enrollment;  automatic  voter registration. 1. The board of
  elections shall, promptly and  not  later  than  twenty-one  days  after
  receipt   of   a  voter  registration  or  pre-registration  application
  submitted pursuant to title nine of this article by a voter  registering
  or  pre-registering  for the first time, send any such voter who did not
  enroll in a party a notice and a form to indicate party enrollment. Such
  notice shall offer the voter the opportunity to enroll with a  party  or
  to decline to enroll with a party and contain the following statement in
  prominent  type  "ONLY ENROLLED MEMBERS OF A POLITICAL PARTY MAY VOTE IN
  THAT PARTY'S PRIMARIES." Such form shall provide a clear alternative for
  the applicant to decline to affiliate with any party.
2. Notwithstanding subdivision two of section 5-304 of this title,  if
  a  voter  who  registered to vote for the first time (or pre-registered)
  pursuant to title nine of this article responds to the  notice  required
  by subdivision one of this section and elects to enroll in a party, such
  enrollment  shall take effect immediately. However, any pre-registrant's
  registration shall  remain  classified  as  "pending"  until  the  voter
  reaches the age of eligibility.
3.  If  a  voter  appears at a primary election and votes by affidavit
  ballot indicating the intent to enroll in  such  party,  such  affidavit
  ballot shall cause the voter to be enrolled immediately in that party if
  the  board  of  elections  determines  that  the  voter  registered  (or
  pre-registered) to vote for the first time pursuant  to  title  nine  of
  this article.
4.  If  a  voter  appears at a primary election and votes by affidavit
  ballot indicating the intent to enroll in  such  party,  such  affidavit
  ballot  shall  be  cast and counted if the board of elections determines
  that the voter registered (or pre-registered) to vote at least ten  days
  before  that  primary  pursuant  to  title nine of this article and such
  voter is otherwise qualified to vote in such election.
Structure New York Laws
Article 5 - Registration and Enrollment of Voters
5-300 - Enrollment; Generally.
5-302 - Enrollment; Completion.
5-304 - Enrollment; Change of Enrollment or New Enrollment by Previously Registered Voters.
5-306 - Enrollment; Correction Of.
5-308 - Enrollment; Automatic Voter Registration.
5-310 - Enrollment; Forms of Affidavits, Mailing Requirements.