D&C 81

 The Lord revealed - 

"...hearken to the calling wherewith you are called, even to be a high priest in my church, and a counselor unto my servant Joseph Smith, Jun.;

2 Unto whom I have given the keys of the kingdom, which belong always unto the Presidency of the High Priesthood..."  (Doctrine and Covenants 81:1–2)

Even though the president of a quorum or presidency holds priesthood keys, I believe then the presidency as a quorum hold priesthood keys even though the counselors do not hold keys individually.  I don't remember a written declaration coming only from the president of the Church.  It is usually comes from the First Presidency.