During his campaign, President-elect Trump vowed to scrap various Obama Administration environmental laws and initiatives. Once in office, the Trump Administration has several avenues to pursue these goals, depending upon the procedural status of the law or initiative.

For those existing environmental rules that are being challenged in court, the new administration could compel the Department of Justice to stop defending the rules and/or ask for a stay in the proceedings for an opportunity to conduct notice-and-comment rulemaking to amend or withdraw the rules. For example, the Waters of the U.S. (WOTUS) rule, which defines the scope of waters protected under the Clean Water Act could be subject to this treatment by the Trump Administration. Challenges to the WOTUS rule by several states and industry groups have been consolidated in the Sixth Circuit, which ruled that it has jurisdiction to hear the challenge earlier this year. The rule was stayed nationwide on October 9, 2015. During a speech on September 15, 2016, President-elect Trump signaled his intention to eliminate the WOTUS rule, calling it one of "our most intrusive regulations."

The Clean Power Plan rule, which was stayed by the Supreme Court as of February 9, 2016, pending judicial review by the D.C. Circuit, is another rule that could be subject to this treatment and is a rule that has also been specifically targeted by President-elect Trump. The rule is a key part of the Obama Administration's efforts to meet the country's obligations under the Paris Agreement, a global accord to combat climate change signed by President Obama in September that went into effect on November 4, 2016. The rule was promulgated by the Environmental Protection Agency (EPA) and establishes greenhouse gas emissions standards for new, modified, and reconstructed coal-fired electric generating units and parameters for states to regulate existing electric generating units.

Finally, the Methane rule is another EPA rule that could be subject to this treatment. The rule was finalized in the Federal Register on June 3, 2016, and establishes new emissions standards for methane and volatile organic compounds (VOCs) for certain activities across the oil and natural gas source category. The Methane rule is also part of the Obama Administration's efforts to meet obligations under the Paris Agreement and to reduce methane emissions from the oil and natural gas sector by 40-45% below 2012 levels by 2025. States and industry groups have challenged the Methane rule in the D.C. Circuit.

President-elect Trump may also use executive orders to nullify, withdraw, or amend non-rule actions President Obama has authorized. President-elect Trump could, for example, by executive order attempt to unilaterally withdraw the U.S. from the Paris Agreement. The U.S. participation in the Agreement was authorized by executive order. Article 28 of the Agreement, however, specifies that any country wanting to withdraw from the Agreement after signing has to wait four years. Thus, for the Paris Agreement, immediate withdrawal may be problematic. The degree to which President-elect Trump could immediately undo other Obama Administration executive actions depends, in part, on whether a federal agency has initiated formal notice-and-comment rulemaking. For example, in August 2013, President Obama issued Executive Order 13650 relating to chemical safety and security, spurring both the Occupational Safety and Health Administration (OSHA) and the EPA to initiate rule revisions to the Process Safety Management (PSM) standard and the Risk Management Plan (RMP) regulation, respectively. While EPA published a proposed rule in March 2016, and accepted public comments, OSHA has not initiated formal notice-and-comment rulemaking for a proposed rule. Consequently, it would be easier for the new President to halt revisions to the PSM standard by executive order than the RMP regulation by notice-and-comment rulemaking.

In addition, to the extent that recent rulemakings are targeted, they can be disapproved by Congress and the President. Under the Congressional Review Act (CRA), before new rules can take effect, all federal agencies are required to submit a copy of the final rule and a report detailing the reasons for its promulgation to Congress. 5 U.S.C. § 801 et seq. (1996). The CRA delays the effective date of all "major" rules for 60 calendar days after they are submitted to Congress or after they are published in the Federal Register, whichever date is later. Id. The CRA is a complex statute that involves various timeframes, procedures, and alternatives, but basically it allows Congress time to review the rule and adopt a joint resolution of disapproval, which it could submit to the President for consideration. Id. If the President vetoes the joint resolution, the rule would become effective unless Congress overrides the veto within thirty session days after the President's veto. Id. Thus, final rules promulgated by the Obama Administration that are subject to CRA review by Congress at the time President-elect Trump takes office, could be disapproved by Congress and the new President. For example, EPA has approved plans to publish final rules that provide flexibility for hazardous waste generators, but the rules have not yet been published in the Federal Register. See KEAG Bulletin No. 2016-15 – EPA Issues Final Rule on Hazardous Waste Generator Improvements. The rule generally would decrease regulatory burden on hazardous waste generators, so it is unlikely that a Republican Congress and President would disapprove the rules, but if the final rule is promulgated soon in the Federal Register, as expected, it could be subject to the CRA review process and possible disapproval.