Trump's border wall joins 31 other national emergencies currently in effect

President Trump's "national emergency" declaration to complete construction of his multibillion-dollar wall along the U.S.-Mexico border Friday came as a shock to some Americans.

There is less than $1.4 billion in the budget deal the Senate and House approved on Feb. 14 — enough for just 55 miles of new barriers and fencing, significantly less than the 200 miles of wall Trump was hoping to start putting up. In order to accomplish his goal, Trump is reportedly prepared to use his executive authority to gain access to roughly $6.6 billion in Pentagon and Treasury Department funds.

HOW TRUMP'S BORDER WALL WILL BE FUNDED

Trump is already anticipating a legal battle, which will likely test the powers of all three branches of government. House Speaker Nancy Pelosi, D-Calif., has already said she "may" consider filing a legal challenge to Trump's call for a national emergency.

"We will have a national emergency, and we will then be sued," Trump said, adding that the federal appeals courts could well rule against his administration. "Then we’ll end up in the Supreme Court, and hopefully we’ll get a fair shake, and we’ll win at the Supreme Court ... just like the [travel] ban.”

WHAT IS A 'NATIONAL EMERGENCY,' AND HOW CAN TRUMP USE IT TO FUND A BORDER WALL?

This isn't the only national emergency active in the U.S.

The president has the power to take such an action — detailed in the National Emergencies Act of 1976 — if he or she believes the nation is "threatened by crisis, exigency, or emergency circumstances (other than natural disasters, war, or near-war situations)," according to a 2007 Congressional Research Service (CRS) report. In the past 43 years, presidents have declared at least 58 states of emergency (not including weather-related events).

Currently, there are at least 31 national emergencies in effect. Here's a running list, according to the Brennan Center for Justice.

Jimmy Carter (2 national emergencies declared, 1 remains active)

• Blocking Iranian Government Property (November 1979)

Bill Clinton (17 national emergencies declared, 6 remain active)

• Proliferation of Weapons of Mass Destruction (November 14, 1994)
• Prohibiting Transactions with Terrorists Who Threaten to Disrupt the Middle East Peace Process (January 1995)
• Prohibiting Certain Transactions with Respect to the Development of Iranian Petroleum Resources (March 1995)
• Blocking Assets and Prohibiting Transactions with Significant Narcotics Traffickers (October 1995)
• Regulation of the Anchorage and Movement of Vessels with Respect to Cuba (March 1996)
• Blocking Sudanese Government Property and Prohibiting Transactions with Sudan (November 1997)

George W Bush (13 national emergencies declared, 11 remain active)

• Blocking Property of Persons Who Threaten International Stabilization Efforts in the Western Balkans (June 2001)
• Continuation of Export Control Regulations (August 2001)
• Declaration of National Emergency by Reason of Certain Terrorist Attacks (September 2001)
• Blocking Property and Prohibiting Transactions with Persons who Commit, Threaten to Commit, or Support Terrorism (September 2001)
• Blocking Property of Persons Undermining Democratic Processes or Institutions in Zimbabwe (March 2003)
• Protecting the Development Fund for Iraq and Certain Other Property in Which Iraq has an Interest (May 2003)
• Blocking Property of Certain Persons and Prohibiting the Export of Certain Goods to Syria (May 2004)
• Blocking Property of Certain Persons Undermining Democratic Processes or Institutions in Belarus (June 2006)
• Blocking Property of Certain Persons Contributing to the Conflict in the Democratic Republic of the Congo (October 2006)
• Blocking Property of Persons Undermining the Sovereignty of Lebanon or Its Democratic Processes and Institutions (August 2007)
• 8 Continuing Certain Restrictions With Respect to North Korea and North Korean Nationals (June 2008)

Barack Obama (12 national emergencies declared, 10 remain active)

• Blocking Property of Certain Persons Contributing to the Conflict in Somalia (April 2010).
• Blocking Property and Prohibiting Certain Transactions Related to Libya (February 2011)
• Blocking Property of Transnational Criminal Organizations (July 2011)
• Blocking Property of Persons Threatening the Peace, Security, or Stability of Yemen (May 16, 2012)
• Blocking Property of Certain Persons Contributing to the Situation in Ukraine (March 2014)
• Blocking Property of Certain Persons With Respect to South Sudan (April 2014)
• Blocking Property of Certain Persons Contributing to the Conflict in the Central African Republic (May 2014)
• Blocking Property and Suspending Entry of Certain Persons Contributing to the Situation in Venezuela (March 2015)
• Blocking the Property of Certain Persons Engaging in Significant Malicious Cyber-Enabled Activities (April 2015)
• Blocking Property of Certain Persons Contributing to the Situation in Burundi (November 2015)

Donald Trump (4 national emergencies declared, 3 currently active)

• Blocking the Property of Persons Involved in Serious Human Rights Abuse or Corruption (December 2017)
• Imposing Certain Sanctions in the Event of Foreign Interference in a United States Election (September 2018)
• Blocking Property of Certain Persons Contributing to the Situation in Nicaragua (November 2018)

Fox News' John Roberts, Brooke Singman and The Associated Press contributed to this report.