If you say "It is illegal for me, ajross, to purchase stale2002's house".
And then I respond by saying "No, it is not illegal for you to do that. All you have to do is get me to agree to sell you the house"
And then your response to this is by saying "But you aren't selling your house!"
This final response by you, does not prove the first statement you made to be true.
It continues to be legal for you to purchase my house, if I agree to it. Just like it continues to be legal for a rancher to purchase land from the government, if they agree to it.
Just because you are not very good at convincing the government/state legislator to sell you that land, does not make it illegal for you to purchase the land from them, if they choose to sell it to you.