I doubt the Ca DoJ would answer a question like that sight unseen. CalGuns has flow charts which go through the assault weapon laws. As noted, there were some items which were banned by name and it might be a simple coincidence but if you have an item on that list as the basic receiver, etc., even if no longer in the same configuration. even if non-semi now, there could be confusion. I'll assume you have already determined whatever hoops need jumping for importation or at least transportation through Customs. That might suggest overall length and barrel length are acceptable? I'd also expect that whatever casing you use for air transport will be suitable for vehicle transport. Since you are arriving in CA, you'll likely drive through CA, Nevada and maybe a touch of Arizona to get to Utah - or fly direct. While the state laws may vary, like Ca., has different rules for a rifle (long guns) as compared to pistols or assault weapons (per our definitions), one would always be safe observing federal laws for traveling with a firearm. Basically, unloaded, locked and stored out of reach of the passenger compartment. I believe not visible from outside is part of the Fed requirement but even if not, would certainly be a good idea. Once you leave Customs, there is no reason to expect anyone would be checking your baggage or contents. Short of an incident like an accident, or something like that.