The ILAB (International League of Antiquarian Booksellers) Code of Ethics governs our approach to the question of ethical business practice. See http://www.ilab.org/eng/ilab/code.html.
Of particular relevance to our business is the point about Preservation:
Members are committed to the preservation of historical materials and should not break complete and intact copies of books or manuscripts.
We wholeheartedly endorse this principle and do not, and do not knowingly deal with individuals or businesses who engage in this practice. The leaves we offer for sale are, to the best of our knowledge, sourced from what are known in the trade as "wrecks". These are books that have suffered the ravages of time; dis-bound, or damaged by insects, water, fire, rough handling etc. The undamaged leaves are "rescued" and traded, as they have been for centuries.
We play our part in the preservation of the leaves for future generations by presenting them protected in a mat, using museum-standard methods and materials.
It is worth noting that a complete and intact Book of Hours is generally worth much more on the antiquarian market than the amount obtained by selling the leaves off individually.