Trump has attempted to coax Republicans into voting his way on the issue and painted those who vote against him as standing with House Speaker Nancy Pelosi and for crime and open borders.
White House spokeswoman Mercedes Schlapp would not say when the veto would happen, but told reporters Friday Trump is "doing what he believes is his constitutional duty, which is to protect the American people".
Brevard County Sheriff Wayne Ivey stood behind President Donald Trump as he signed the first veto of his presidency. "Watch, when you get back to your State, they will LOVE you more than ever before!" he said.
Trump offered praise to the GOP senators who remained loyal and voted against terminating his declaration, saying "they were very courageous yesterday, and I appreciate that very much". That declaration was an effort to circumvent Congress to secure more money for his southern border wall. When no deal came, Trump declared a national emergency on February 15 to get the funding without congressional approval.
American Civil Liberties Union, which filed one of the cases, said the veto was meaningless - like the declaration in the first place. In a statement, Republican senator Lamar Alexander of Tennessee said: "Never before has a president asked for funding, Congress has not provided it, and the president then has used the National Emergencies Act of 1976 to spend the money anyway".
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The Democratic-controlled House of Representatives had passed the resolution to overturn the emergency last month, and 12 Republicans sided with Democratic Senators to clear the Senate in a 59-41 vote on Thursday afternoon.
The resolution was approved in the aftermath of the killing of US-based Saudi journalist Jamal Khashoggi in the Saudi Consulate in Istanbul on October 2, 2018.
"House Republicans will have to choose between their partisan hypocrisy and their sacred oath to support and defend the Constitution", she added. He explained the legality of Donald Trump's countermeasure.
"I think actually a national emergency was designed for a specific goal like this, so we have a great case", Trump said. "They shouldn't even be suing, but they will because they always do".
"The President acted well within his discretion in declaring a national emergency concerning the southern border", wrote Assistant Attorney General Stephen Boyd, setting out the legal basis for the proclamation under the National Emergencies Act and additional statutory authorities, which largely tracks an internal memo issued by the Office of Legal Counsel at the Justice Department.