I guess this context was in Meiji era. See: http://www.google.co.th/search?hl=th&biw=1280&bih=569&q="ord...

When you break up 開拓使令書, you know this is composed of following two words:
開拓使 reclamation commissioner
令書 command paper

On 開拓使, you find its definition here (among others):
http://suido-ishizue.jp/kindai/hokkaido/02.html

On 令書 Given historical background of your text, this document comes only from Meiji Emperor, so 勅令書 would be more accurate, but we go by your original text.

If it was to form a company (reclamation company), and that permission came from a monarch (such as Emperor or King), then the document is called "Charter". But this does not apply to your case.


HTH

I believe that this is related to the appointment of development commissioners (開拓使) during the early Meiji Era via (imperial) rescript (詔勅). These offices were established both to modernize Japan and also to secure the country (through development) against the aspirations of imperial Russia. I have included some links below related both to a famous development commissioner (Kuroda) and the wider push to modernize Japan through the use of foreign advisers.