President Trump faces a court decision to use extraordinary powers to build a wall on the American border with Mexico .
California and New York said they would take legal action to challenge its move to bypass the Congress and provide funding for the project.
Wall construction was the key to Mr. Trump's campaign.
Democrats said it was a "gross abuse of power" and promised to challenge it "using all available means of redress."
Mr. Trump signed the emergency declaration together with the draft law on expenditure to prevent a repeat of the recent closure of the government. Emergency announcements can give him access to billions of dollars. Mr Trump announced the plan after the Congress refused to finance the wall.
During the first few hours the first case against the declaration of a national emergency was put forward. and three Texas landowners, who were told that the wall could be built on their properties.
How did the Democrats answer?
Governor Gavin News of California rejected the president's decision as a "political theater."
"He was embarrassed, and his base needs to be fed," he told reporters.
"Fortunately, Donald Trump is not the last word, the courts will be the last word," he added. The New York State Democratic General Attorney Leithia James said the state would not "stand up for abuse of power and will be punished with every legal instrument we possess."
The American Civil Liberties Union (ACLU) said it would sue in the coming days to curb this "shoutingly unlawful enforcement action".
Two senior Democrats, Speaker of the House of Representatives Nancy Pelosi and Democrat Democrat Chuck Sumer, said that they were challenging "the seizure of power by the disappointed president" in Congress and in the courts.
"Illegal statement the president of a crisis that does not exist, does great violence to our Constitution and make America less safe, theft of urgently needed defense assets for the safety of our military and our nation" [1
Analysts that this remark could undermine Mr Trump's case that
What did Mr Trump say?
Announcing the announcement in the White House of the Pink Garden, the president said that an emergency would allow him to get nearly $ 8 billion per wall.
is expected to be diverted from military construction projects and existing efforts to combat drug trafficking.
This is still considerably less than the estimated cost of walls worth $ 23 billion at almost 2000 miles of the border.
Trump acknowledged that he was able to sue the Government for the move, and predicted that extraordinary rendition would lead to a lawsuit that would most likely end in the Supreme Court.
"We will face a national security crisis on our southern border," he said.
"We have intrusion of drugs, invasion of the gang, human invasion,
" Everyone knows that the walls are working. "
Later, Mick Mullwini, the Chief of Staff of the White House, told reporters that Step Truman "creates a zero precedent."
has already been referred to the court. It's not like he just did not get what he wanted to waving with a magic wand and taking a bunch of money,
A Dangerous Case
John Sopel, editor of BBC North America
The nuclear issue is a fall that was presented as a guerrilla guilty
On one side of the wall are Republicans, on the other, Democrats, and the President made him more difficult than this. Many Republicans in the Senate and in the House are deeply restless about what Mr Trump does.
This is a great occupation of the land by the president, which undermines their position and creates a very dangerous precedent.
Can the Congress stop the Trump's extraordinary step?
The Emergencies Act contains an item that allows the Congressional Term State to state a state of emergency if both chambers vote for it – and the president will not veto.
Democrats could accept such a resolution to the Senate with a comfortable majority of the Chamber's members. The Republicans control the Senate, but a number of Republican senators are loudly concerned about the President causing a state of emergency in the country
. Sen. Maine Susan Collins, who said that this move has "questionable constitutionality."
However, the resolution still needs to be signed by Mr. Trump, which will allow him to veto. To overturn the presidential veto requires an overwhelming majority in both houses of Congress.
What is a National Emergency?
The National Emergency Law is intended for the time of the national crisis. Mr. Trump claims that there is a migration crisis on the southern border of a country – a statement that is strongly refuted by experts on migration. Announcement of a national emergency will give the president access to special powers that will allow him to actually circumvent the usual political process, and he will be able to divert money from existing military or disaster relief budgets to pay for the wall
. The emergency declarations of previous presidents were mainly used to resolve foreign policy crises, including blocking terrorist connections, access to funds, or the prohibition of investment in human rights abuses.
Mr Trump's decision to use powers to overcome the partisan impasse through border security has hit politicians on both sides of the passage of deviation from the alleged use of the act.
"This would be a very dramatic extension of how it was used in the past," said Republican senator Ron Johnson.