This act -- one of his first as the nation's 43rd president -- effectively blocks a spate of Clinton's executive orders intended, among other things, to create a number of new national monuments.

Clinton issued a flurry of environment-related executive orders during his final weeks in office, such as a measure designed to limit water pollution generated by factory farms. Since the orders cannot take effect until they have appeared in the Federal Register for a certain amount of time, however, the memo may mean those orders are never implemented.

The memo also directs the department heads to "temporarily postpone the effective date" of all regulations that have been published in the Federal Register, but which have not yet taken effect. That provision, which will stretch over a period of 60 days, renders moot a host of environment-related measures, such as a recently unveiled U.S. Environmental Protection Agency rule that mandates a 95 percent reduction in harmful diesel emissions by 2006.

Moreover, the memo calls on the nation's independent regulatory agencies to "voluntarily" suspend all new and pending rule-making efforts until they can be reviewed by the Bush administration. The memo declares that such a suspension would advance "the interest of sound regulatory practice," and would help to stave off the onset of "costly, burdensome, or unnecessary" regulation.

The memo sets in motion the Bush administration's long-held pledge to conduct a "vigorous review" of the myriad executive orders and other non-legislative federal regulations that were promulgated in the final weeks -- and even hours -- of the Clinton administration. Four weeks before the November election, for example, the Clinton administration was placing an average of 210 pages of regulations per day in the Federal Register, one of the highest rates ever recorded.

A number of Republican lawmakers on Capitol Hill had been sharply critical of the Clinton administration's regulatory actions, especially those that were put forth by agencies such as the U.S. Environmental Protection Agency (EPA). Oklahoma Senator Jim Inhofe decried the Clinton administration EPA for trying to "cram through scores of rules and other regulatory decisions without proper disclosure," a practice that Inhofe called "irresponsible and wrong."

Other Congressional Republicans went further, vowing to roll back many of the environmental protections initiated by the Clinton administration. Utah Congressman Jim Hansen has promised to undo the National Monuments that Clinton designated across several Western states, and to return the public lands to their former management status.

Hansen, the new chairman of the House Resource committee, last week announced that his Congressional panel will scrutinize the rules and regulations implemented by the Clinton administration "that may have violated federal law" or "circumvented established procedures."

The directive put forth by President Bush on Saturday only elicited more apprehension among conservation advocacy groups, many of which have long feared that the former Texas governor will enact policies disastrous for the nation's environment. Frank O'Donnell, executive director of the Washington-based Clean Air Trust, worried that Bush's memo was the first step toward undoing the EPA's newly enacted diesel emissions rule.

"Given the massive health benefits of the diesel cleanup, it would be a terrible blunder for the new administration to weaken or delay these new standards," O'Donnell said.

The EPA's new diesel rule, which falls within procedural parameters of the regulatory suspension put forth by Bush on Saturday, would prevent some 8,300 premature deaths each year, according to EPA scientists. The rule, by lowering emissions from heavy duty trucks and buses, would also stave off the onset of more than 20,000 cases of bronchitis and 360,000 asthma attacks annually, EPA scientists claim.

Those factors may or may not exempt the EPA's diesel emissions measure from the reach of the Bush administration's new regulatory suspension, which exempts any rules pertaining to "emergency or other urgent situations relating to health and safety."

One EPA official, requesting anonymity, told ENS that the agency is "trying to figure out" which regulatory actions might be subject to the memo, and which measures might be exempted.

"We have not made any final decisions on a lot of pending regulations, and whether they're subject to this or not. At this point, nobody can say which rules might be pulled back," the official said.

The White House could not be reached for comment on the Bush administration's new regulatory review plan as of late Monday.