A senior Justice Department official is arguing that 3- and 4-year-olds can learn immigration law well enough to represent themselves in court, staking out an unconventional position in a growing debate over whether immigrant children facing deportation are entitled to taxpayer-funded attorneys.Jack H. Weil, a longtime immigration judge who is responsible for training other judges, made the assertion in sworn testimony in a deposition in federal court in Seattle. His comments highlighted the plight of thousands of juveniles who are forced to defend themselves each year in immigration court amid a surge of children from Central America who cross the southwestern U.S. border.