Fetch!

Hi,

One may not instruct his dog to go outside and bring in an object, where the space is not enclosed by an eruv. This is part of the law requiring that our animals rest on Shabbat.

There is room to contend that where an animal brings in an object on its own, one may use the object. However, there are grounds to prohibit as well, both in terms of having one's animal perform a prohibited act on Shabbat, and in terms of marit ayin (the appearance of wrongdoing).

(Rivivot Ephraim 1:231)

Have a great day,
Mordechai