In ArcGIS Desktop 10 I have an arc that has violated the topology rule that the road feature should not extent outside of my boundary. I tried to use the clip tool in editor but cannot complete the clip. I should be able to click on the boundary, then use the trim tool to clip off the extended line. I selected the boundary, its lit up and shows in the TOC as selected, but nothing happens with the clip tool and I can't do anything with the offending road feature that is over the boundary line.
Clip and Trim are two different commands. If you select your boundary and then go to Editor > Clip, all editable features (on all editable layers) will be cut back to the boundary line. The Trim command won't work in this case because your arc touches the boundary at two points - this tool works with overshoots rather than overlaps. To use it you would first have to break your arc outside the boundary and then trim each remaining leg separately back to the boundary.