If you prune them that's the end of them for this season. No flowers, no branching. I know this from experience. A son with a football taught me.

Been there, done that and agree 100% with floral. Pinching or cutting back the stalk will only result in no flowers. Have broken them off myself accidentally, dog has done the same but deer are the biggest culprit for reducing the height of my lilies, buds or no buds!!

True lilies such as Casa Blanca do not branch, so pruning/pinching them will not make them do what you are hoping for. There are some lilies that are shorter -- the Pixie line, for instance -- and the Asiatics will be shorter generally than the Orientals. I suggest if your Casa Blancas are too tall for their location that you move them to another spot and get some shorter lilies as replacement. Good luck!

Thank you all - glad I asked! I will move them. Or plant more things around them to support them. I have so much trouble with critters eating bulbs and nothing has discovered these for some reason, so I was hoping there was a non-moving solution, as they may not remain uneaten if I disturb them.