Caba,
And, since JWs often ignore requests not to call back (except when it's done formally) I think some regulation of repeated visits by JWs could be feasible.
In other words, they have the right to call once but they do not have the right to make repeated calls if the householder objects.
That's correct. The first time let them slide, but repeated calls they should be fined if the house holder says not to call again. This would require that the JW keeps better records of who not to call on, and never call again not excluding a call to see if they still feel the same way about not calling.