President Trump is moving to restructure the nation’s energy future to block any transition away from fossil fuels. And he is testing the boundaries of presidential power to do it.

The orders that Mr. Trump signed on Monday would make it easier and cheaper for companies to produce oil and gas and for the government to stop clean energy projects that have been approved.

While some actions lie within his purview, others may violate federal law or run counter to judicial decisions. Among other things, Mr. Trump raised the possibility of reversing the Environmental Protection Agency’s authority to regulate greenhouse gases, which has been confirmed by the Supreme Court, and proposed to halt funding for electric vehicle charging stations that Congress has already authorized.

“Congress passed landmark infrastructure and climate investments, and now President Trump is attempting to illegally withhold that money from American businesses, communities, and workers,” said Representative Frank Pallone, Democrat of New Jersey.

The moves also underscore a fundamental tension. Mr. Trump declared that the United States is facing an energy emergency, yet wants to block thousands of megawatts of planned wind projects that could power homes and businesses. He talks about strengthening American manufacturing but plans to withdraw assistance from the electric vehicle industry, which has invested billions of dollars in new factories across the United States.

“The phrase ‘energy emergency’ is an excuse to put in place initiatives that are hostile to the energy transition that is already taking place, to stop the progress that has been made in producing solar and wind power, electric vehicles, batteries, and renewable power,” said Robert N. Stavins, director of the Harvard University Environmental Economics Program.