Dealing with a resident who does not wish to merge
What happens if one of the residents of the adjacent properties is Jewish and does not admit to the validity of the laws of Eruv, such as a Sadducee, or a Kuti, or a Mumar: Eruvin 61b, 68b-69b
Forcing a homeowner to merge his yard with another one, if it will not cost him anything and it will help the other person: Eruvin 49a
What happens if one of the residents regularly merges, and opts not to one week: Eruvin 80a