RIYADH, Saudi Arabia—A senior Saudi cleric issued a religious ruling to allow fathers to arrange marriages for their daughters "even if they are in the cradle," setting up a confrontation between government reformers and influential conservative clergy.

Sheik Saleh al-Fawzan, one of the country's most important clerics, issued the ruling after the Justice Ministry said this month it would act to regulate marriages between prepubescent girls and men in the Islamic kingdom.

"Those...