LAST week the Environmental Protection Agency unveiled stringent new regulations on smog, and it’s crystal clear the agency has legal authority to impose these rules. The E.P.A. also recently announced an initiative to reduce greenhouse gases from power plants, though its legal authority to regulate emissions that cause global warming is murky. Some states will sue to block the plan; years of litigation may be in the offing.

Here’s the rub. Smog has been decreasing steadily, down 18 percent since 2000 and 33 percent since 1980. Greenhouse-gas accumulation in the atmosphere is increasing steadily. Yet perversely, the federal government has a well-defined authority to act on the environmental issue that’s getting better, but not on the one that’s getting worse.

Our major environmental laws are a generation or more out of date — written for conditions of the past, not the present. The Clean Air Act, signed by President Richard M. Nixon in 1970, has not been amended since 1990, a quarter-century ago. The Clean Water Act, passed in 1972, has not been updated since 1987. The Endangered Species Act, passed in 1973, was last amended in 1982. The National Environmental Policy Act, the law that mandates environmental impact statements, was passed in 1970 and last amended in 1982.

Or take our myriad recycling programs. Many such initiatives were set in motion by the Resource Conservation and Recovery Act, passed in 1976 and not substantively amended since 1986. When Congress approved this legislation, it was believed the country was running out of primary materials, and of landfill space. Both assumptions turned out to be false, but the federal law, and its local derivatives, live on.