Yeah the rangers can ask to look in your pack or gear. but you have the right to tell them no. If you do they will not press it further unless they have witnessed you doing something illegal like picking some plants or something.
The one thing I haven't heard talked about in all of this is what is next for Lynn Camp Prong. Are they going to do some large follow up shocking? Obviously they can't shock the whole stream so what if there are more rainbows in there? Are they going to run the poison again and start over or just wait and hope for the best. I have heard a lot from the fisheries folks on how terrible it is and all the stuff they are going to do to these people that they will never catch, but not any strategy at all on how this may be handled from the fish management perspective which is a bit dissappointing.