Greenwire: In drought-stricken California, lawyers are asking a simple question with a complicated answer. Can the state take away water rights? At issue: the U.S. Constitution's 5th Amendment, which says no property shall be taken without just compensation. So if California gets more aggressive in requiring irrigation districts -- and particularly so-called senior rights holders, whose claim to divert and use water dates back more than a century -- to curtail water use, some property rights lawyers think...