Eight state attorneys general have joined together to sue the nation's five largest public utilities. The goal: to force a 3 percent annual reduction in carbon dioxide emissions (search) over the coming decade.

The problem, however, is that none of the utilities are located in any of the eight states, and that the AG's have neither the authority nor the responsibility to act in the broader national interest—as they are claiming to do.

In fact, the party with that authority and responsibility — the U.S. government — has enacted federal statutes that preempt state laws. The Clean Air Act (search), passed 41 years ago after vigorous debate and deliberation, is enforced by the Environmental Protection Agency. Today, Congress is considering another bill, introduced by Sens. John McCain, R-Ariz., and Joseph Lieberman, D-Conn., that would cap CO2 emissions.

The public interest is best served when federal and state regulation is complementary, not duplicative or conflicting. Yet, the AGs, led by New York's Eliot Spitzer (search), have decided to supersede the role of the federal government, intending to press forward with a trendy legal theory known as "public nuisance," (search) which holds defendants liable for any "unreasonable" interference with rights common to all members of a community.

According to Spitzer, the theory is "well-established and unambiguous." Tell that to courts across the nation that have been struggling with the public nuisance concept as applied to gun manufacturers and fast-food distributors. Whenever "unreasonable" is part of the definition, there's bound to be ambiguity as judges and juries try to cope with technically complex (and disputed) science, as well as disagreements over health risks and costs of abatement.

When the federal legislature is asked repeatedly to enact pollution regulations, the resultant regulations, or their rejection, control legal claims. It is not up to the courts to trump the determination of elected lawmakers with respect to an issue on which the views of those lawmakers have been expressed over and over again. If a determination is to be made that CO2 emissions must be reduced, the Congress must make that determination, not the courts.

Spitzer's apparent frustration at the failure of the legislature to endorse the laws he favors is not sufficient to engage the judiciary in an effort to implement a more restrictive set of rules.

To be sure, conservatives and libertarians (search) ordinarily favor common law solutions, tailored to the unique problems of individual litigants, over legislative solutions based on an inflexible, command-and-control regime. But the common law alternative is no longer appropriate once the federal government has dominated the legal landscape.

Moreover, common law actions are typically private actions, not state-sponsored litigation. Indeed the Audubon Society of New Hampshire and the Open Space Institute in New York filed a lawsuit similar to Spitzer's on the same day that he filed. Even if it were proper to circumvent the federal government, state-sponsored litigation is plainly redundant.

Here are the rules that the AGs ought to follow before exposing defendants to double-and-triple-jeopardy from public and private lawsuits under both federal and state laws:

— First, do not litigate on behalf of private parties who, on their own, have unhindered access to the courts — either singly or as part of a class action.

— Second, pursue only those claims related to residents collectively or to a state's overall economy, not particular parties who might be tempted to instigate special-interest litigation.

— Third, seek money damages, not conduct remedies. The problem with conduct remedies is that they invariably affect out-of-state interests.

— Fourth, do not sue if a federal agency is also suing, unless there are state-specific injuries that are not addressed in the federal suit.

— Finally, avoid claims that federal regulators have considered and rejected. The underlying problem is straightforward: Economic losses from excessive, overlapping regulation can cause immense damage to both producers and consumers.

That said, there is one principled ground on which Spitzer and his fellow AGs could legitimately intercede. They could argue — with support from constitutional scholar Randy E. Barnett, among others — that the Clean Air Act and other federal anti-pollution statutes are unconstitutional.

The Commerce Clause (search) was originally meant to cover only interstate trade, not manufacture or agriculture. Accordingly, the regulation of pollution, which stems from manufacture and agriculture, but not trade, is beyond the enumerated powers of Congress.

If so, pending a constitutional amendment that authorizes federal environmental legislation, the AGs can proceed with their anti-pollution crusade. Don't hold your breath waiting for Spitzer and friends to make that argument.

Robert A. Levy is senior fellow in constitutional studies at the Cato Institute. His latest book, Shakedown: How Corporations, Government, and Trial Lawyers Abuse the Judicial Process, will be published by the Cato Institute in 2004.