Complete and unquestioned recognition of one government by another as being legal and legitimate. Most states have governments recognised by most other states and the United Nations and are thus considered to have de jure control.
De jure control is, in some sense, an artifact of the present perspective on state sovereignty. When states are nominally treated as being equal to one another - in terms of things like the right to territorial control and non-intervention in domestic affairs - states that don't necessarily have the capacity to exercise sovereignty nevertheless possess it on paper.
Constrast with de facto control