J.B. Van Hollen, the state attorney general, said after the decision that it may help Wisconsin win a federal challenge to the law. But Lester Pines, a lawyer who represented the League of Women Voters, said the court gave no directions on how the state is supposed to implement its "saving construction" to the law.
"I find that to be very odd," Pines said. "I find it to be unworkable and it's going to lead to more litigation."
The state currently provides free ID cards but requires applicants to present certified birth certificates, which cost $20.
The court ruled in two lawsuits challenging the ID law, with a 4-3 decision in one case and 5-2 in the other. The National Association for the Advancement of Colored People is also trying to overturn the law.
Wisconsin is currently barred from enforcing the law. A federal judge ruled it unconstitutional in April, a decision now under appeal.
Van Hollen said he hopes the "saving construction" will allow Wisconsin to begin enforcing the law this November.