As it stands that statement opens up a lot of questions.
Not in cattle country it doesn’t. Many western states still have open range designated areas. No rancher can keep up 100’s of miles of fencing, 100% of the time. Cattle push old fenceposts over using them for scratching posts. And in treeless NoDak, every fencepost is a scratching post.
The laws in these states have long required ranchers to report stray cattle to the sheriff’s department so their brand can be identified and their owner notified. Not to mention that the owner might have notified the sheriff regarding missing cattle and their suspected whereabouts.
The Brossarts appear to have been engaging in a little opportunistic cattle rustling. Just hang on to the 3 cows until they’ve weaned the calves then mingle the calves with your own and brand them. You are now 3 calves richer and their mothers can be turned out on the side of the road to wander off again.