Is swearing a false oath in court to save the rights of the oppressed considered a "ghamus" oath (a sinful, diving oath) and does it necessitate expiation?

Lying is forbidden, and swearing an oath upon it is even more forbidden. It is not permissible except in cases of necessity. The yameen al-ghamūs (the immersive oath) is a false oath. If you swore that you did not speak with a group of people with whom you have actually spoken, then this is a yameen al-ghamūs. The majority of scholars hold that there is no expiation for it because it is among the major sins (kaba'ir), and its obligation is repentance and seeking forgiveness. Whereas the Shafi'is believe that expiation is obligatory (feeding ten poor persons, clothing them, or freeing a slave; or fasting three days if one cannot find any of these). This ruling applies unless the oath led to saving a Muslim, their property, or a benefit that could not be achieved except through it. If the lie was to save a Muslim's property taken unjustly, then lying is obligatory in this case.