The most commonly quoted definition of the political principle of subsidiarity is that given by Charles Handy in his 1998 book The Hungry Spirit:
Subsidiarity is the principle that decisions and responsibilities should lie as low down in the system as possible.
In essence, this is the principle that the decision-making process should be brought as close as possible to the people directly concerned. In other words, if a local matter clearly only affects those living in the local area, there should be no interference from national government, and decisions should be left to whatever local representatives are in place. This is close to the aim of Green Parties that all political, social and economic decisions should be taken at the lowest effective level. It is also an important principle in the workings of the European Union, whereby the international jurisdiction of EU bodies is supposed to be limited to matters which are of common concern to all member states. In practice, of course, there is ongoing debate as to which areas should be devolved to which levels of government.
Subsidiarity, however, is not just about devolution to local governments at various levels, but also requires a recognition that certain decisions must be made at a level which represents all of those affected. Local representatives, for example, cannot be allowed to simply decide to shift their problems into another locality. If, for example, a region requires a landfill, waste incinerator or other undesirable development, the decision as to where to build it could not be left to the local councils of each locality within the region, as this would result in the development being built nowhere (see BANANA). The decision as to in which locality the development should be sited must be taken by a regional authority, having regard to the needs and concerns of everybody living in that region.
Thus, a true system of subsidiarity would see environmental decisions, which affect the welfare of the planet as a while, being taken at a global level. To a certain extent, this can happen, as with the various recent summits on global warming. However, as we can see from the unfortunate decision of the US Government on the Kyoto Protocol, unilateral action by individual states or interests can still scupper such efforts.