the same time and place, it is likely that they influenced one another. As with water rights, mining rights could be forfeited by nonuse. The miners codes were later legalized by the federal government in 1866, and then in the Mining Law of 1872. The Homestead Act of 1862 granted legal title to the first farmer to put public land into agricultural production. This first in time right to agricultural land may have been influenced by appropriation theory applied to mineral lands. In recent years, there has been some discussion of limiting air pollution by granting rights to existing pollution sources. Then it has been argued, a free cap and trade market could develop in pollution rights. This would be prior appropriation theory applied to air pollution. Recent concern over carbon dioxide and global warming has led to an economic market in CO2 emissions, in which some companies wish to balance emissions increases by offsetting decreases in existing emissions sources. This is essentially acknowledging a prior appropriation right to existing CO2 emitters. See also Air rights Countryside and Rights of Way Act 2000 (in the UK) Crown land (see "Logging and mineral rights" under Canada) Easement ("the right of use over the real property of another") Land rights Right of public access to the wilderness Riparian water rights United States groundwater law Civil law (legal system) References External links Western States Water Laws BLM site. Law and economics Environmental economics Water law in the United States