Is it permissible to prevent an unjust father from entering the house, and is that considered an act of disobedience?

The injustice, disobedience, or even disbelief of a father does not permit one to be undutiful towards him. Children are commanded to treat their parents with kindness and to accompany them in a good manner. Allah Almighty says: "And We have enjoined upon man [care] for his parents. His mother carried him with hardship upon hardship, and his weaning is in two years. Be grateful to Me and to your parents; to Me is the [final] destination. But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them but accompany them in [this] world with appropriate kindness and follow the way of those who turn back to Me [in repentance]. Then to Me will be your return, and I will inform you about what you used to do." (Luqman: 14-15). Preventing a father from entering the house is not an act of righteousness. Allah Almighty says: "And your Lord has decreed that you shall not worship except Him, and to parents, good treatment. Whether one or both of them reach old age [while] with you, say not to them [uff] and do not repel them but speak to them a noble word. And lower to them the wing of humility out of mercy and say, 'My Lord, have mercy upon them as they raised me when I was small.'" (Al-Isra: 23-24). One must show dutifulness to the father and treat him kindly while advising him gently, seeking help from righteous people if beneficial, and persistently supplicating for his guidance.