Not even could. It wasn't a campaign event and they were not there in any official capacity to support a candidate for public office.

Asking the sitting president to sign a hat is not even remotely a breach of protocol.https://t.co/DKrQ9FAYyl https://t.co/mBBZMHTRkL

— Geoffrey Ingersoll (@GPIngersoll) December 27, 2018
.....