Getting a rape conviction can be tough under the best of circumstances. Victims are reluctant to come forward, there are rarely witnesses, and even when physical evidence was collected, it can also be viewed as evidence of consensual sex.

But when the accused is a foreign national who takes refuge in an embassy and invokes treaties that supersede local law, prosecutions get even more complicated.

In this case, the accused are six American Marines and the accuser is a 22-year-old Filipina woman. The alleged attack took place earlier this month in the Subic Bay area of the Philippines, where the Marines were participating in Philippine-U.S. military exercises.

Though preliminary charges have been filed by a district prosecutor's office, the Marines are being kept by the U.S. government at the American Embassy. And that isn't sitting well with many Filipinos, including rape-victim advocates and people already uncomfortable with the U.S. military influence there. Demonstrations by Filipino groups were planned in major U.S. cities this week.

The men are accused of raping the woman in a van after meeting her at a karaoke bar. She was later found by the road by passersby who took her to police. She told police she had had drinks with the men earlier and lost consciousness during the attack. She said she didn't know how many men
had raped her.

The six men are members of a Marine unit based in Okinawa, Japan. The Visiting Forces Agreement between the United States and the Philippines says U.S. troops visiting for military exercises are under the primary jurisdiction of the U.S. government when there are criminal offenses "arising out of any act or omission done in performance of official duty." The agreement calls for the Philippines to waive jurisdiction over a case if U.S. military authorities ask with possible exceptions if a case is considered of particular importance to the Philippines.