MONTPELIER, Vt. (AP) — As colleges wrestle with how to address sexual assault, a legal challenge involving a small Vermont institution brings an obscure part of the equation to the fore: how to report, investigate and punish sexual assaults that happen in overseas-study programs.

Statistics on such assaults are scant, although no one disputes they occur. The federal requirements for schools to report and investigate sexual assaults overseas can be murky. And since perpetrators and victims can be from different schools or studying through programs run by other institutions, colleges' options on punishing students internally can be tricky.

Responding to critics' arguments that campus sexual assaults are underreported, state governments and even Congress are beginning to take steps to better monitor those crimes, and are specifically including overseas study programs.

"These are real things that colleges and universities are thinking about," said Joseph Storch, associate counsel for the State University of New York system, who regularly travels the country to discuss the legal questions around study-abroad programs. "There are no simple answers."

Middlebury College, a private, 2,500-student liberal arts college at the foothills of the Green Mountains, found out the hard way that punishing a student accused of sexual assault is easier said than done.

On the first day of classes this September, a federal judge ordered the school to readmit a student it had expelled for a sexual encounter that occurred overseas; the country has not been named. The accuser came from another school; the two were studying abroad through a program run by Vermont's School for International Training.

The Middlebury student, referred to in court documents only as John Doe, argued he had been cleared of wrongdoing by an investigation conducted by SIT. But after he returned to campus last winter, Middlebury did a separate investigation, and he was expelled over the summer.

Court documents do not say whether the incident was reported to police in the country where it occurred.

Doe sued Middlebury for breach of contract and got a federal judge to issue a preliminary injunction so he could return to school. Middlebury is appealing to the 2nd U.S. Circuit Court of Appeals in New York and has asked for a quick hearing.

"As this case moves forward, I think universities will pay attention to how the court determines whether SIT's investigation was sufficient or Middlebury College's secondary investigation was sufficient," said Michael Pfahl, associate counsel at Kent State University in Ohio, who has studied legal issues raised by student conduct abroad.

While the number of American students studying abroad has skyrocketed in the past two decades — from 71,000 in 1991-92 to 289,000 in 2012-2013 — there are no comparable data for sex assaults in those programs, said Brian Whalen, president of the Forum on Education Abroad, which is tracking such crimes.

Partly in response to the shortage of data, the forum developed what it calls a critical incident database, tracking everything from sexual assaults to robberies to gastrointestinal illnesses. The first set of results, released this year, covers calendar year 2014.

The report found 18 incidents of sexual assault from a pool of only about 10 percent of U.S. students studying abroad — relying on data from 350 programs in 101 countries. That means the total number is likely much higher.

Applying U.S. federal law on the investigation and reporting of sexual assaults and other incidents abroad — such as Title IX, which among other things requires schools to have procedures for investigating sexual assaults, and the Clery Act, which requires schools to report on-campus crime — is complicated.

U.S.-based institutions with foreign campuses must report sexual assaults that occur there, but they are not required to distinguish which were in study-abroad programs or on which overseas campus.

In 2013, the most recent year for which Department of Education data are available, only one sex offense was reported at a foreign campus of U.S.-based four-year institutions. But the vast majority of overseas-study programs don't take place on foreign campuses of U.S.-based colleges; they're usually on the campuses of foreign-based institutions.

As colleges and governments seek to stem sexual assaults, overseas-study programs are sometimes being specifically included, something that could lead to more accurate statistics.

Minnesota lawmakers this year required the secretary of state to publish links to publicly available reports that detail sexual assaults and other crimes affecting students in study-abroad programs. New York passed a law setting standards to address violence that applies to students in the state's public and private colleges and universities, both at home and abroad.

And Congress is considering a bill, proposed by New York Democratic Rep. Sean Maloney, that would require schools to report crimes and other incidents that occur while students are studying abroad and make sure the schools have adopted policies to protect students from harm.

"I think there's been a great amount of effort by a lot of different colleges and a lot of different organizations in the study-abroad field to really get this right," said New York's Storch. "It's not that we want to be harder on these students. We want to get it exactly right."

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Associated Press writer Jennifer C. Kerr in Washington contributed to this report.