What are the legitimate Shar'i justifications for disinheriting an heir?

There is no legitimate religious justification for parents to deprive any of their heirs of inheritance. Inheritance has its causes and impediments. If the causes are present and the impediments are absent, no one has the right to prevent it. Allah Almighty Himself ordained inheritance and distributed the estates, and He clarified the shares in His Book, warning whoever transgresses His limits with His saying: "These are the limits [set by] Allah, and whoever obeys Allah and His Messenger will be admitted by Him to gardens [in Paradise] under which rivers flow, abiding eternally therein; and that is the great attainment. But whoever disobeys Allah and His Messenger and transgresses His limits - He will put him into Fire to abide eternally therein, and he will have a humiliating punishment." Therefore, changing Allah's ruling indicates displeasure with what Allah has apportioned, and it warrants a humiliating punishment.