Brown made a point of recruiting fugitive slaves and free blacks to be part of his raid
With the rise of colonies in the Americas and their need to incorporate laborers, Europeans focused their attention to Africa, and some asserted that the Transatlantic Slave Trade would make it possible for Africans to make contact with Christianity and 'civilisation'.
For this reason, religion was an important driver during slavery period, since Africans slaves, after their arrival to the Americas, were subject to different methods to make them more docile, being Christianity a crucial part.
This question is meant as your personal opinion however based upon the laws and if you agree on them or not yes the government should be able to because the post office is a government owned agency therefore is run by the government and anybody working with him there is an employee of the city state and essentially the government