Seif al-Islam is charged by the international court with crimes against humanity for his alleged involvement in the deadly crackdown on dissent against his father's rule.
However, Libyan authorities who captured him last year insist that the international tribunal's own rules allow them to try Seif al-Islam.
Under the Hague-based court's founding statute, it can only step in if a country where crimes were committed is unable or unwilling to prosecute, a legal principle called complementarity.