This event all happened about 5 minutes at 3 PM in Washington. I got a violation ticket for seatbelt when I set in the back set of private car. When we stopped our car and before the officer came, I was trying to find my husband's international driver license, so I unlocked my seatbelt, therefore I also got one ticket. The officer came to front window and asked license and said 'do you know you are overspeed?' Before he came, I set on the middle of backseat, I unbelted in order to find some stuff I need and move closer to the window when the car stopped. But the officer just ask and took our license away. When we cool down I and our mother waved our hand and try to get the officer back, but he just ignored!
Foreigner or not, if you get fined, you are responsible for paying the fine.
However, you can dispute the fine in court if you disagree, eg. in this case you had a pretty good excuse for not having your seatbelt on. The exact procedure, the time and effort needed to do it, and the likelihood of getting the fine waived will vary greatly based on where this happened.