920. One Who Gave Up His Rights Then Carried Anyway

Eiruvin 2:5

Just as a homeowner can forgo his ownership rights in favor of another homeowner in the same courtyard, the residents of one courtyard can forgo their ownership rights in favor of the residents of another courtyard. The recipient of these rights can then cede them back to the original owner. The result is that if two people share a courtyard and neither has made an eiruv, the first may forgo his ownership rights in favor of the other, enabling the second to carry in the courtyard until he has completed what he needs to do. The second person may then return the ownership rights to the first. Rights may be exchanged back and forth in this manner several times over the course of Shabbos. One may forgo ownership rights in a ruin the same way that one does in a courtyard.

Eiruvin 2:6

What if a person who has forgone his ownership rights transfers an object into or out of the domain that he ceded? If he did so intentionally, his actions prohibit the other residents from carrying because he didn't live up to the arrangement he made with them. If he transferred an object unwittingly, he does not prohibit the others’ ability to carry because he did stick to the arrangement. This is the case only when the other residents did not yet utilize the rights that were granted to them. If the other residents have already utilized these rights, his actions do not impede their ability to carry whether he acted intentionally or unintentionally.