What remedy does the thrower have if another perhaps belligerent player in the group says he is not going to move his cart (let's say bad blood brewing during round)? This extends to the Catrina incident at TX States where the player who owned the car blocking her stance was not able to move his car? The penalty to the player with the equipment is simply a courtesy warning. But Catrina could not take relief moving backwards per the casual relief rule. Is the thrower just screwed being forced to take an Optional Rethrow penalty and moving back to their previous lie if they can't get the object moved or the player to move it (short of a fight)?
The truck in Catrina's incident is a lot different than a bag or cart belonging to a player in the same playing group as the affected player. No one knew who the truck belonged to, so moving it was impractical. And because of its unfortunate position, casual relief on the line of play didn't give her any better of a stance/lie since there was just as much in-bounds space on the other side of the truck as there was on the side where her disc was at rest.
For a player in the same group, if he refused to move his bag/cart due to some bad blood or whatever, I'd start with giving him a courtesy warning officially for refusing to act in accordance with a rule. If it is a matter of his bag/cart blocking my ability to take a stance, I'd then go ahead and move it out of my way whether he liked it or not. My right to move it is covered by the casual relief rule...there's no specificity on who can move a casual obstacle if it can be moved. If it's a matter of potentially interfering with my shot, I'd go ahead and throw and if his bag/cart in any way interferes with the shot, I'd penalize him the two throws proscribed by the rule.
Not sure why I'd need any more recourse than that provided to me by the rules. If things escalate beyond the courtesy warning, he's likely going to put himself in danger of disqualification because there's no way this incident doesn't get reported to the TD.