The U.S. Supreme Court will begin today to consider a lawsuit over private property development in Lake Tahoe that has had lot owners and land-use planners squared off for more than two decades. At issue is a 1981 moratorium on the development of certain lots where runoff from rain and snowmelt would pollute the lake. The moratorium affected several hundred families, many of whom hoped to retire to Lake Tahoe but have been unable to do anything with their lots but pay taxes on them. The families sued, asking the California-Nevada planning agency that imposed the moratorium to compensate them for delays in being able to use the land. Environmentalists worry that a ruling in favor of the Tahoe lot owners would set an alarming precedent and create huge liabilities against the government for thinking green.