Alaska Purchase: Can Russians cancel this deal?

Russia sold Alaska to the States in 1867 for $7,2 mln. This is history as we know it. But nonetheless, some Russians still question whether the deal was legit. In fact, people are so confused, they address president Putin: "Can Russians get the North American colony back?". So if this question keeps rising over and over again there must be some reason? Surely Russian Alaska can become reality once again? Let’s find out together once and for all.