Texas Sen. Ted Cruz addressed the Texas Public Policy Foundation’s second annual energy and climate change summit, where he said “the president’s radical attempt to destabilize the nation’s energy system is flatly illegal.”

“And unless it is invalidated by Congress, struck down by the courts or, hopefully, rescinded by the next administration,” Cruz continued, “it will cause Americans’ electricity costs to skyrocket at a time when those who are struggling can least afford it. What the Obama administration is doing to harm the American economy is the sort of power grab that our founders would have recognized as tyranny.”

Last week, Cruz joined 51 Senators, including presidential candidate Kentucky Sen. Rand Paul in voting for a resolution of disapproval against the President’s Clean Power Plan. South Carolina Sen. Lindsey Graham and Florida Sen. Marco Rubio both missed the vote.