Desks, heavy chairs, railings, the judge's bench, and such are obstacles. You will have to move around them if action is necessary, and they can be useful in impeding the movement of an assailant, providing hard and sharp surfaces to throw an assailant against, or possibly even as cover or concealment.
Pens, clipboards, briefcases, light chairs, and such are weapons. You can move these items to suit your purposes. These items can be used to attack an assailant, to block an assailant's attack, to trip an assailant, or to cause distraction. Unfortunately, all of these uses are available to an assailant as well as to you, so be careful around moveable objects, and consider all the different ways they can be used.
The next time you are in court, a conference room, someone's office, or whatever arena you visit in your practice, look around at the items in your environment and consider these uses.