A Pennsylvania judge blocked a new state police policy regarding the sale of partially manufactured gun parts that could be used to create working firearms.

Commonwealth Court Judge Kevin Brobson issued the preliminary injunction over the policy Friday.

The move came three weeks after Pennsylvania state police issued guidance to gun dealers on how to conduct background checks for sales of parts that are often called 80 percent receivers or unassembled “ghost guns,” according to The Associated Press.

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Brobson ruled the businesses that create and sell gun frames — the plaintiffs in the lawsuit — raised legitimate questions over the vagueness of the policy. He added that he would be open to revising the scope of his injunction based on the police’s response.

“The harm of threatened enforcement of an unconstitutionally vague policy, derived from statute, cannot be remedied after the fact,” Brobson wrote.

Joshua Prince, a lawyer for the plaintiffs, told the AP he was happy with the ruling and that the police policy could lead to unjust criminal and civil penalties “in relation to something that not even the Pennsylvania State Police could define.”

The state police this month announced that dealers are required to call the state gun-purchase background check system for sales of the "ghost guns" and cannot rely solely on the use of the online system.

The new guidelines came after state Attorney General Josh Shapiro ruled that the “ghost guns” are firearms under state law.