In his state of the union speech this February, President Obama vowed,

If Congress won't act soon to protect future generations, I will. I will direct my cabinet to come up with executive actions we can take, now and in the future, to reduce pollution, prepare our communities for the consequences of climate change, and speed the transition to more sustainable sources of energy.

President Obama followed through on that promise today, unveiling a climate action plan that includes measures to reduce greenhouse gas emissions, accelerate renewable energy permitting on public lands, and prepare American infrastructure for the impacts of climate change.

The centerpiece of the plan is the announcement that the US Environmental Protection Agency (EPA) will regulate greenhouse gas emissions from existing power plants, in addition to the rules already in draft form that are set to regulate emissions from new power plants. The White House released a video to explain the importance of these steps in addressing climate change by decarbonizing the economy.

Republican House speaker John Boehner reacted to this news by calling the EPA regulations "absolutely crazy." However, in reality they're required by law.

Under the Bush Administration, the EPA refused to regulate greenhouse gas emissions. The state of Massachusetts sued the EPA, and the case went all the way up to the US supreme court. In 2007, in a 5-4 decision with Justice Anthony Kennedy casting the deciding vote along with the four more liberal justices, the court ruled that if greenhouse gases were determined to endanger public health or welfare, the EPA would be required to regulate their emissions in accordance with the Clean Air Act.

The Bush EPA delayed the decision about the threat of greenhouse gas emissions until after he left office. After President Obama took office, the EPA issued its endangerment finding in 2009. Based on an evaluation of the best available scientific evidence like the Intergovernmental Panel on Climate Change (IPCC) report and US national climate assessments, the EPA determined that greenhouse gas emissions clearly endanger public health and welfare via their impacts on climate change.

This finding meant that under the Clean Air Act, greenhouse gases meet the definition of "air pollutants," and the EPA would have to regulate their emissions from mobile and stationary sources (vehicles and power plants). Vehicle emissions were regulated via new fuel efficiency standards requiring cars and light trucks to average 54.5 miles per gallon by 2025. The newly announced power plant emissions are the EPA's enforcement of the Clean Air Act requirements for stationary sources.

On the one hand, with Congress refusing to implement any sort of climate legislation, regulating emissions from vehicles and power plants is the biggest single step President Obama can take to reduce American greenhouse gas emissions. He could have followed the Bush administration's strategy and tried to delay these regulations, forcing environmental groups to sue to make the courts require that the EPA enforce the law.

On the other hand, that is really all the Obama administration is doing – enforcing the law. Any opposition complaints that this decision is "crazy" or bypassing Congress are factually and legally wrong.

In fact, if Republicans want to eliminate these regulations, all they need to do is pass climate legislation to supersede them. A growing number of conservatives support implementation of a carbon fee and dividend system, for example. At the moment the majority of Republicans in Congress seem to deny that climate change is human-caused and/or a problem, and oppose taking any steps to reduce greenhouse gas emissions.

However, there are now only two options available to them – let the government regulate greenhouse gas emissions, or pass climate legislation. Philosophically, Republicans generally oppose government regulations and support free-market solutions like carbon pricing; however, it appears that congressional Republicans would rather force the Obama administration to regulate emissions and then accuse them of "killing jobs", as Speaker Boehner already has.

On the contrary, studies have shown that EPA regulations generally have a modestly positive impact on the economy and jobs. A national study by the University of Massachusetts at Amherst also found that every dollar invested in clean energy creates two to three times as many jobs as putting that same dollar into coal, oil, and natural gas.

Ultimately the Obama administration deserves credit for implementing these greenhouse gas regulations in a timely manner rather than delaying as the previous administration did. His emphasis on the importance of decarbonizing the economy to address the threat of climate change in a comprehensive climate action plan is a major step towards addressing the threat of climate change. It's also important to remember that these regulations are required by law, and if congressional Republicans don't like them, they should propose a better solution of their own.