Senator Mitch McConnell of Kentucky has begun an aggressive campaign to block President Obama’s climate change agenda in statehouses and courtrooms across the country, arenas far beyond Mr. McConnell’s official reach and authority.

The campaign of Mr. McConnell, the Senate majority leader, is aimed at stopping a set of Environmental Protection Agency regulations requiring states to reduce carbon pollution from coal-fired power plants, the nation’s largest source of greenhouse gas emissions.

Once enacted, the rules could shutter hundreds of coal-fired plants in what Mr. Obama has promoted as a transformation of the nation’s energy economy away from fossil fuels and toward sources like wind and solar power. Mr. McConnell, whose home state is one of the nation’s largest coal producers, has vowed to fight the rules.

Since Mr. McConnell is limited in how he can use his role in the Senate to block regulations, he has taken the unusual step of reaching out to governors with a legal blueprint for them to follow to stop the rules in their states. Mr. McConnell’s Senate staff, led by his longtime senior energy adviser, Neil Chatterjee, is coordinating with lawyers and lobbying firms to try to ensure that the state plans are tangled up in legal delays.

On Thursday, Mr. McConnell sent a detailed letter to every governor in the United States laying out a carefully researched legal argument as to why states should not comply with Mr. Obama’s regulations. In the letter, Mr. McConnell wrote that the president was “allowing the E.P.A. to wrest control of a state’s energy policy.”

To make his case, Mr. McConnell is also relying on a network of powerful allies with national influence and roots in Kentucky or the coal industry. Within that network is Laurence H. Tribe, a highly regarded scholar of constitutional law at Harvard Law School and a former mentor of Mr. Obama’s. Mr. Tribe caught Mr. McConnell’s attention last winter when he was retained to write a legal brief for Peabody Energy, the nation’s largest coal producer, in a lawsuit against the climate rules.