Common Pool Resource
See called Common Property Regime
Definition
From the Wikipedia at http://en.wikipedia.org/wiki/Common_Property_Resource
"The terms common-pool resource (CPR), alternatively termed a common property resource, is a particular type of good, and a natural or human-made resource system, whose size or characteristics of which makes it costly, but not impossible, to exclude potential beneficiaries from obtaining benefits from its use. Unlike pure public goods, common pool resources face problems of congestion or overuse, because it is subtractable.
The term "common property regime" refers to a particular social arrangement regulating the preservation, maintenance, and consumption of a common-pool resource. The use of the term "common property resource" to designate a type of good has been criticised, as common-pool resources are not necessarily governed by common property regimes."
Mark Cooper:
"These resources are non-excludable, but they are rivalrous. The solution to the problems associated with common-pool resources is not necessarily private property, though. “If exclusion costs are comparatively high, common ownership solutions may be preferable.” The possibility of co-existence of different governance regimes is particularly important for common-pool re-sources because many CPRs incorporate characteristics of private and public goods. In some instances, this is known as the “comedy of the commons.” The “comedy of the commons” is the opposite of the “tragedy of the commons” – the notion that users of commonly held property such as forests, fisheries, and most notably air, work together to ensure that overexploitation does not occur." (http://cyberlaw.stanford.edu/system/files/From+Wifi+to+Wikis+and+Open+Source.pdf)