How can one be disinherited legally?

Laws vary from state to state. In most a person can be mentioned in a will with the comment that the person is legally disinherited.

Some states will not allow you to do this for a spouse or a minor child and have provisions to take care of them even if your will says otherwise.

Another way is to transfer all of one's real property reserving a life estate and listing the persons you choose to have your property as remaindermen. Upon your death the fee will be owned free and clear of the life estate by the remaindermen.

There is also a living trust