I'm not sure if we have a status of forces agreement with the new government of Libya, I pray that we do or Libya's Interior Ministry will be able to do as they want with these four service members (Most likely US Marines). I hope this situation is straightened out soon before something happens to them.
For those of you who don't know what a status of forces agreement is, it is a protection for American service members serving overseas, in case they are accused of a crime in the host country that the host country agrees the service member will be tried by the United States military and not the host country.
The reason for a status of forces agreement is that some country's punishments for some crimes can be quite harsh compared to the United States judicial system, for example in some nations the punishment for a first time DUI can be death, or for theft the penalty could be the cutting off of your hand.
These status of forces agreements also mean that US service members fall under US laws in many cases, for example now that it is allowed for openly gay service members can now serve in the open, in some nation these men and women serve homosexuality is actually illegal in their judicial system. This status of forces agreement keeps them safe while serving say in Saudi Arabia.
Official: 4 U.S. military personnel detained by Libya - CNN.com