You get to specify that the trolley doesn’t have brakes because you can say “I will only apply the conclusion I am getting from the trolley problem in real life situations that are similar to the trolley problem in that there are no (metaphorical) brakes.”
The equivalent for your slavery contract is “I will permit slavery only in situations where I will starve if a slavery contract is not allowed”. You can’t do this, because you can’t have a slavery law that applies only in a specific, unlikely, scenario. A law permitting slavery will apply in the vastly more common scenario where the slaver is still incentivised to get some money from you and sell you the food.
You get to specify that the trolley doesn’t have brakes because you can say “I will only apply the conclusion I am getting from the trolley problem in real life situations that are similar to the trolley problem in that there are no (metaphorical) brakes.”
The equivalent for your slavery contract is “I will permit slavery only in situations where I will starve if a slavery contract is not allowed”. You can’t do this, because you can’t have a slavery law that applies only in a specific, unlikely, scenario. A law permitting slavery will apply in the vastly more common scenario where the slaver is still incentivised to get some money from you and sell you the food.