First Presidency says only church members can receive the second anointing.
Joseph F. Smith, John R. Winder, and Anthon H. Lund, Letter to Oleen N. Stohl, 22 May 1908; rep. Devery S. Anderson, ed., The Development of LDS Temple Worship, 1846–2000: A Documentary History (Salt Lake City, UT: Signature Books, 2011), 152
People who are not members of the Church during their lifetime are not eligible to receive second blessings. They should not only have been members of the Church, but their faithfulness and worthiness to receive these blessings should be unquestioned.