I get that one, pretty cut-and-dry, you can't merge or change lanes into someone. Your second part however, is a little more subjective. Given the "normal and reasonable movement of traffic" at that particular moment in time is slow/standstill, one could argue that they were in compliance, especially if they had signaled to merge back into the left lane. Secondly, "stopping or reduced speed is necessary for safe operation or to comply with law", one could argue they felt their recourse for safe operation was to come to a complete stop in order to safely merge in the left lane. I don't know offhand what laws are applicable to construction zone signage and what legal weight a "Right lane closed, merge left" orange sign has, but if I were to feel like I wanted to play 'traffic cop du jour', I should have legal merit to sit in the right lane with the intent to merge left (ie. sit there in the right lane with my left turn signal on) in order to comply with the signage. No? Whether I actual merge or not is my choice, but in the eyes of the law, safety and complicity are the key words and I could debate I was acting in accordance with both. Especially the safety verbiage. Unless there's some case law to refute the subjectivity of safe operation of a motor vehicle?