As this legal framework makes clear, emergency powers are not a license for the president to sidestep Congress. To the contrary: The only powers the president can access during a national emergency are those Congress has granted. However potent some of these powers might be, the source of the president’s authority in all cases remains a legislative delegation—one that is granted in advance because true emergencies require immediate action. A president using emergency powers to thwart Congress’s will, in a situation where Congress has had ample time to express it, is like a doctor relying on an advance directive to deny life-saving treatment to a patient who is conscious and clearly asking to be saved.

Of course, Trump’s hesitation also belies his claim that there is an emergency at the border. Presidents don’t dawdle in the face of real emergencies. President George W. Bush did not spend weeks scratching his head about whether to issue an emergency declaration after the terrorist attacks of 9/11. But even if a real crisis existed, emergency powers are designed for situations in which Congress has no time to act. If Congress does have time, then there is no justification for bypassing the ordinary legislative process.

Read: What the president could do if he declares a state of emergency

Indeed, the more time Congress has to act—and the more times it votes against providing the funding the president has asked for—the clearer it becomes that an emergency declaration in this case would be designed as an end run around the Constitution. Article I provides that “no Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.” This provision is one of the Constitution’s most important checks against executive-branch overreach. Congress has now consistently declined to appropriate funding for the border wall. Whatever deference judges might owe to the president’s assessment of what constitutes an emergency, an interpretation of the National Emergencies Act that would allow the president to engage in an expenditure of funds for which Congress has expressly withheld consent cannot be squared with the Constitution.

Trump is right about one thing: He should give Congress time to debate, deliberate, and vote. But if Congress continues to vote against providing funding, that is a decision the Constitution commands the president to respect. The National Emergencies Act is not—and was never intended to be—a constitutional workaround for a president who cannot bend Congress to his will.