How can we have unalienable rights and take them away if they are unalienable?

You can't. "It is important to understand that the very premise of our nation is the fact that these rights, based on Natural Law, are "God-given." If they are not given to us by an Authority higher than human government, then any government action to abolish those rights would be against God's will. Rights that are subject to government restriction or license are called a privilege rather than a right."