how to stop crawling of https:// urls from google

While checking through the indexed pages of my site, I found lots of urls with https:// are indexed by Google. It is creating content duplicity as I found two cached version of the same page, one with http:// and another with https:// .

I checked for the reason and discovered that there are some links present in my site with https:// . I can't stop posting of such urls as I don't have any control over my visitors.

So my questions are:

1) How do I stop google from crawling the https:// urls?
2) How do I remove the urls that are already indexed with https:// ?

Please help me with your valuable suggestions asap. I'm in need of it.