Why did Quintus Metellus Numidicus go into exile in 100 BCE?

In 100 BCE, Quintus Caecilius Metellus Numidicus went into exile to avoid being forced to swear an oath of support for an agrarian law proposed by the tribune Lucius Appuleius Saturninus.12

The legislation, which involved land distribution and colonial settlements, had been passed through the assembly with blatant illegality. While other senators eventually complied with the requirement to swear to observe the law, Metellus refused to do so, objecting to the irregular manner in which the bill had been enacted. By choosing to retire to Greece, he effectively forestalled potential condemnation in a treason court, though he was later officially exiled.2