Ya, cannabis seeds are and have been an excellent food source for a long time. Here's a link:
http://www.ratical.org/renewables/hempseed1.html

Seeds of the plant cannabis sativa, hemp seed, contain all the essential amino acids and essential fatty acids necessary to maintain healthy human life. No other single plant source has the essential amino acids in such an easily digestible form, nor has the essential fatty acids in as perfect a ratio to meet human nutritional needs.