BYU is private property. The most they can do to a non-student is to trespass them from that property.
Almost all of the buildings on campus are used as houses of worship, so 76-10-530 might come into play. The penalty is so insignificant though, why worry.
If you are a student, however, they can and probably will expel you if you are found to be packing. I carried for 2.5 of my 3.5 years there, however.