Yes, the Firearm Owners Protection Act was a federal law intended to protect lawful firearm owners when traveling through potentially more restrictive areas. So long as the person isnt otherwise prohibited from owning a firearm, and its legal in both the state the journey originated in and the destination, and the journey is primarily
through the more restrictive state or local jurisdiction in question with only minimal required stops in transit, they are not supposed to be subjected to legal penalties while transiting through that state or area.
Heres more info
https://chuckfranklinlaw.com/interstate-travel-with-guns/
Ive seen much incorrect info regarding firearms and travel over the years, much of it may have had some origin in truth many many years ago, but so much has changed in the past 20 or so years. There are in fact some quite restrictive state laws, but being aware of them and taking basic precautions not to cross those legal lines goes a long ways towards staying out of trouble. California restricts semi-auto detachable magazine fed rifles (the so-called assault rifles), some east coast states have similar bans and also restrict handguns in some ways, and at least New jersey does not allow possession of hollow point handgun ammo. But the mere possession of a firearm in accordance with applicable laws shouldnt be an issue in through transit.
It used to be common knowledge that Illinois was very strict about firearms, and hard on people with firearms in vehicles in many instances, however.....court cases and other things like passage of concealed carry laws in the majority of states including Illinois have changed the picture.