Legal concepts of mineral ownership and the nature of the property rights in oil and gas, including the theories of absolute ownership in place, qualified ownership, and so-called non-ownership, are discussed. Classification of the principal oil-producing states is made according to the theory of ownership prevailing in each.

The principal legal effects are attributable to different theories of ownership, including restrictions upon the creation and duration of estates in oil and gas separate from estates in the surface. The origin and operation of the lessee's obligation reasonably to develop the leased premises and to protect them from drainage are given. Circumstances are outlined under which the lessee's rights may be terminated, and the liability for trespass is discussed. The new theories of development are based on increased knowledge of geology, such as unitization and community operations. Expert testimony by the geologists on the administration of these phases of the law is important.

Oil and gas conservation programs have legal aspects which include both the substantive laws and their actual administration. Validity of restrictions upon production and drilling operations is largely dependent on their reasonableness in the light of geological information.

There are certain legal rights and obligations incident to geophysical prospecting, selection leases, liability for trespass, et cetera.