While slave codes were in effect,
enslaved people’s activities were not restricted.
enslaved people could enter in legal contracts.
enslaved people could not be legally punished.
enslaved people’s activities were restricted.

I believe the answer is: enslaved people’s activities were restricted.

Slave codes dictate a list of activities that the slaves are banned to do in order to give the slave owners with absolute power over their salves. The codes were designed in a way to destroy's the slaves' will to run away or conducting a rebellion toward the owners.

porter is writing economic history because he is focusing on the cost of developing vaccines.

after the roman empire, the catholic church began to unify by taking on many duties of a government.