Full Idea
Many philosophers deny that two numerically distinct physical objects could be 'wholly co-located'.
Gist of Idea
It seems wrong that constitution entails that two objects are wholly co-located
Source
Trenton Merricks (Objects and Persons [2003], §2.III)
Book Reference
Merricks,Trenton: 'Objects and Persons' [OUP 2003], p.38
A Reaction
A fish can be located in a river; the Appenines can be located in Italy. If you accept the objection you will probably have to accept identity-as-composition, or object-eliminativism. One object can have two causal roles, supporting two identities.