"Only then, if that policy is challenged in a court of law, may its constitutionality be evaluated," Brobson wrote.
In 1975, Commonwealth Court issued a permanent injuction saying the PIAA - the state's key policy-making body for interscholastic sports - could not have a rule prohibiting girls from practicing or competing with boys.
The PIAA responded by removing the rule from its bylaws. However, individual schools can choose to set such policies, said Melissa Mertz, PIAA associate executive director.
But a Pittsburgh couple filed suit recently, hoping to have the court revisit the injunction, holding that the increasing presence of boys on their daughters' field hockey games had made a mockery of the competition.
Brobson said he would not tamper with the injunction.
Mertz said the next step would be for counsel to inform the board of the court's decision, probably at the October board meeting.
But she said that any PIAA policies prohibiting mixed-gender competition likely would be challenged, and that mounting a defense could end up being a long and expensive process.
"We'd almost rather leave it the same as it is now," Mertz said.
"Our concern is, we create a policy, we're going to end up in court," she said.
Contact Chris Palmer at 609-217-8305, firstname.lastname@example.org, or follow on Twitter @cs_palmer.
This article contains information from the Associated Press.