Shamar Rinpoche's explanation of the proper use of the titles "Khenchen" and "Khenpo"

Khenpo is a term in the vinaya meaning "the one who gives the monks vows"—one who has demonstrated the highest vinaya conduct and has become very accomplished, a senior monk.  

Khenchen means "Senior Khenpo".

The Kagyu, Nyingma and Sakyapa schools use the title of Khenpo for those who have achieved the highest levels of mastery in Shedras.  Why?  The reason is that in Tibet, the teachers who achieved such mastery also were the ones who gave the monks vows.

However, the term for a teacher who has received the highest levels of teachings is Lob Pon. This title essentially means "teacher." The senior teacher, or principal, is called Lob Chi.

One can be a very good philosophical teacher, or Lobpon, without receiving the full monk's vows.

Teachers who have kept the monk's vows very well, and achieved maturity, can be appointed Khenpo— or "giver of monk's vows." But not until they have proven able to keep the monk's vows can a teacher be appointed Khenpo. 

Over time, the term Khenpo has come to refer loosely to the teachers who receive the highest levels of scholarship in the shedra. 

At the time when Shamar Rinpoche appointed Trinley Paljor to the title of Khenchen, he announced that the title of Khenpo and Khenchen should only be used by those who have demonstrated the highest vinaya conduct and have become very accomplished in this respect.

Therefore, in June 2006, when Shamar Rinpoche reorganized the Karma Kagyu Shedras (in Kalimpong and in Nepal) and appointed the principal of the shedra and the junior shedra teachers, he announced that from now on the term Khenpo should only be used to refer to "a vow giver according to the vinaya," in keeping with tradition, and the title of Lobpon should refer to those who have achieved high academic training and become teachers. 

The following are technical and historical arguments for this practice: 

Example 1: Technical Proof

The title Lob Chi has traditionally referred to the principal of the shedra. If Lob Chi refers to the highest teacher of the shedra, as it has, and the titles of Khenpo simply referred to those who had achieved the highest degree of study, then Khenpo would be below the Lob Chi. How can this be?

Example 2: Historical Proof

At the time when the king of Tibet invited Shantarakshita to give monk's vows to the first 7 monks in Tibet, Guru Padmasambhava was a tantric teacher there. At that point, Shantarakshita was referred to as Khenpo because he was the giver of monk's vows, and Padmasambhava was referred to as Dorje Lobpon, not Khenpo, because he had two consorts and therefore was not a keeper of the full vinaya vows.