Question: A man owns a plot of land. Another man seizes it, claiming it is his. The owner offers fair recourse—litigation before any scholar the usurper chooses, any reputable arbiter he selects, or an oath—but the usurper refuses all of this and insists on going only to judges who are not acceptable, who care only for bribes. In such a case, may the owner repel this aggressor by force, even if it leads to killing?
Answer—and Allah is the One who grants success: What is preferable and closer to God-consciousness is patience. Defending property by killing is not permissible—except in the single case where a person knows with certainty that the property is his, and knows that the one who has seized it is an aggressor with no doubtful claim or pretext—nothing but injustice and aggression.
That said, what predominates in our lands is that none lays claim or seizes anything except that he has some shubha (colorable claim) by which he imagines justification. It is exceedingly rare that someone takes land from another in our lands with no shubha and no pretext beyond sheer might, aggression, and tyranny. Therefore, a person should not—and is not permitted to—defend his land by killing.
Moreover, a rebel’s refusal to litigate before a judge of truth is not a justification for killing him; disciplining the rebel belongs to rulers and authorities, not to adversaries.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2