There have been lots of discussion
http://www.canadavisa.com/canada-immigration-discussion-board/if-nominated-from-a-province-is-there-any-mandatory-time-that-we-have-to-stay-t402681.0.html
The bottom line is
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Every citizen of Canada and every person who has the status of a permanent resident of Canada has the right:
to move to, and take up residence in, any province, and
to pursue the gaining of a livelihood in any province.
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http://www.pch.gc.ca/eng/1356638440337/1356638551250