The order by Judge Dexter M. Thompson Jr. of the Circuit Court for Cecil County bars Mr. O'Malley, a Democrat, from enforcing the executive order he signed last month.
"Continuing to enforce the provisions of ... the executive order would result in immediate, substantial and irreparable harm to the plaintiffs," wrote Judge Thompson. The judge stated he made the ruling because the executive order breeches the separation of powers as detailed in the state constitution and because the independent child care workers should not have a union negotiator forced upon them as a result of the order.
Delegate Michael D. Smigiel Sr., Eastern Shore Republican and an attorney, argued the case.
Mr. Smigiel said he brought the case before the court because the executive branch has been "usurping" the powers of the General Assembly.
"It is a victory for the legislative process and following the [Maryland] Constitution," he also said.
Mr. O'Malley quietly signed two executive orders last month, allowing in-home health care workers and child care providers to form unions.
Mr. Smigiel and others then questioned the constitutionality of the move, saying the governor made an "end-run" around the Assembly by signing the orders.