stored water in California, is most prevalent in the central and southern areas. Additionally, the majority of the state's population is in the south. Water viewed as excess by the south is viewed by the north as environmentally essential for agriculture, fisheries, and wildlife. While the southern electorate has a greater portion of the population it is not as unified in its viewpoint as is that of the north, so ballot propositions such as those promoting a Peripheral Canal to transport water to the south have failed. Land use is also divisive. High land prices mean that ordinary people keep a large proportion of their net worth inland. This leads them to agitate strongly about issues that can affect the prices of their home or investments. The most vicious local political battles concern local school boards (good local schools substantially raise local housing prices) and local land-use policies. In built-up areas, it is extremely difficult to site new airports, dumps, or jails. Many cities routinely employ eminent domain to make land available for development. A multi-city political battle was fought for several years in Orange County concerning the decommissioning of the huge El Toro Marine airbase. Orange County needs a new airport (pilot unions voted the existing airport, John Wayne, the least safe in the U.S.), but the noise could reduce land prices throughout the southern part of the county, including wealthy, politically powerful Irvine. Gun control is another divisive issue, which stems at least partially from the fact that California's constitution does not explicitly guarantee the right for ordinary citizens to keep and bear arms. In the cities, California has one of the U.S.'s most serious gang problems, and in some farming regions, some of the highest murder rates. The state also contains many individuals who desire to keep and bear arms in defense of themselves, their families, and property. The legislature has passed restrictive gun control laws. Private purchase of assault weapons (generally, semi-automatic rifles that look like military rifles) without prior approval from the state Department of Justice (which rarely grants such approval) is a felony. The law does not, however, prohibit sales of semi-automatic hunting-style civilian weapons, leading many to question the effectiveness of the cosmetic distinction. Pistols may be purchased and kept in one's home or place of business (however, they are required to be registered to the state and must be considered a "safe"