He got 64% of the total vote (45 million people). His closest opponent was a communist with 17%.
Now, how much votes did Putin steal? 10%? That would still leave him with twice as much votes as his next opponent. He'd still have the people's mandate.
It is quite possible that you do not like the choice of the majority of Russian people. But if you cannot accept result of a democratic election then you should not be making statements about Constitution and the law.