On a given Friday or Saturday night, few rules govern the festivities within the countless fraternity houses that define the social experience of many American college students.

Similarly murky, it turns out, are the rules that govern how the individual chapters populating these houses relate to their host universities and national Greek organizations — a confusion illustrated by the protracted lawsuit against former members of Yale’s chapter of Sigma Phi Epsilon, as well as the national fraternity, stemming from a fatal incident at a 2011 football tailgate.

At a time when fraternities are under increasing scrutiny — including from lawmakers and the national media — for hazing, sexual misconduct, alcohol and personal injury, the case sheds light on this ill-defined legal landscape and the consequences for Greek activity.

Brendan Ross ’13, a former brother of Sig Ep, was driving a U-Haul truck at the fraternity’s tailgate at the Harvard-Yale game when he lost control of the vehicle and crashed into a crowd of people, killing one woman and injuring two. One of the injured women, Sarah Short SOM ’13, as well as attorneys for the estate of the deceased woman sued not only Ross, but also the Yale chapter of Sig Ep, the national fraternity, U-Haul and Yale University.

The lawsuit claimed that the national organization was vicariously liable for the accident because Ross was acting as an agent of the fraternity. The claim against the University was that it had been negligent in allowing motor vehicles in the tailgating area.

In April of this year, Short settled with the University on undisclosed terms, according to Eric Smith, an attorney with Faxon Law Group, the firm representing Short. The question of the fraternity’s responsibility, however, is still unresolved, as a judge denied the national organization’s request for summary judgment — which would have allowed the judge to make a preliminary determination about liability — and ordered it to proceed to jury trial, scheduled for December.

No matter the outcome of the trial, experts in higher education law said the case illuminates the changing relationship between fraternities, both local and national, and the universities where they set down roots.

Doug Fierberg, an attorney who represents plaintiffs in fraternity misconduct cases, challenged the argument of Brian Warren Jr., the national fraternity’s chief executive officer, that national fraternities have no knowledge of local chapters’ activities — an argument Warren laid out in an October 2013 deposition provided to the News by Faxon Law Group.

Because national fraternities establish detailed bylaws to govern their constituent chapters, including rules regarding risk management, Fierberg said, they bear responsibility when local chapters run afoul of those rules. He added that while many national fraternities have successfully argued against this agency relationship in the past, lawyers and courts have started to realize that “their claims of disconnect … are a charade.”

But Peter Lake, director of the Center for Excellence in Higher Education Law and Policy, disagreed that national fraternities are increasingly to blame for the missteps of local chapters. He said national organizations have successfully demonstrated that they are far removed from daily operations.

Whether those organizations should exert more control over local activities, Lake said, is another question.

More interesting, he said, is the relationship schools maintain with fraternities, though they ultimately do not answer to the college administration. Although the Sig Ep lawsuit did not claim that Yale was responsible for the fraternity’s actions, but rather that it had been negligent in its own tailgate regulations, many lawsuits have emerged over the years that try to hold universities accountable for fraternity hazing or alcohol-related injuries. For example, in the 2012 case Yost v. Wabash College, the Indiana Court of Appeals ruled that Wabash College, along with the school’s chapter of the Phi Kappa Psi fraternity, held no responsibility for the injuries of Brian Yost, who suffered physical and mental injuries after a pledging ritual that forced him to withdraw from school.

When asked how Yale views its relationship to the fraternities on campus, Karen Peart, Yale’s deputy press secretary, said that “although the University doesn’t supervise or govern unregistered fraternities or sororities, it expects students who belong to them to comply with the Undergraduate Regulations, which apply to all students in Yale College.” Yale College Dean Jonathan Holloway has described the college’s authority over Greek organizations as “limited.”

“But as individuals in the organization, they are still Yale students,” he said in the spring. “So if a Yale student is found in violation, we have the full power of the University.”

Currently, Lake said, there are few regulations governing the relationship between universities and fraternities. But as Greek life comes under greater scrutiny, he expects that to change.

“We’re absolutely moving toward a place with more regularized standards,” he said. “Usually a demand for accountability leads to a period of finger pointing, [which eventually] leads to some kind of constructive business relationship. But while people are still in court pointing fingers at each other, students are still waiting for resolutions.”