Same as with their coffee brand they put an emphasis on ecology:
official page:"Love of people, love of the Earth. Bob's ideals and principles centered around one thing, love. And now we're turning his principles into products."
http://www.thehouseofmarley.com/
the principles:
http://www.thehouseofmarley.com/purpose/the-principles
from the news:
http://www.trendhunter.com/trends/house-of-marley
http://www.cultofmac.com/hemp-used-in-b ... 2011/75566