Government lawyers will tell the court the President has clear authority to "suspend the entry of any class of aliens" in the name of national security.
The US President Donald Trump's travel ban will be back before a judge later today.
The controversial ban has been suspended since federal judge James Robart ruled that it was causing “immediate and irreparable injury” - and may be ruled unconstitutional.
A Federal Appeals court will hear testimony later today as the Trump administration tries to get the ruling overturned - and the ban re-instated.
In arguments filed yesterday evening, the Justice Department insisted the executive order was a "lawful exercise."
Government lawyers said the President has clear authority to "suspend the entry of any class of aliens" in the name of national security.
The Justice Department's brief also said that Judge James Robart's suspension of immigration restrictions was too broad.
Yesterday lawyers for Minnesota and Washington made the case for permanently ending the restrictions - which stop people from seven mainly Muslim countries entering the US.
15 more States are also expected to make fresh legal challenges.
The Justice Department has criticised Washington and Minnesota - the two states who launched the legal challenge against the executive order - for asking courts to "take the extraordinary step of second-guessing a formal national security judgment made by the President himself."
A randomly selected panel of judges from the California-based 9th US Circuit Court of Appeals will hear the case.
The Appeals Court decision could itself be the subject of a later showdown in the Supreme Court.
Lawyers representing Washington and Minnesota have warned that resuming the travel ban on migrants and visitors from seven Muslim-majority countries would "unleash chaos again" - separating families and leaving university students stranded.
Their case has also been buoyed by 10 former US officials - including secretaries of state and CIA directors who served under Republican and Democratic presidents - who filed a declaration in the case arguing that the travel ban served no national security purposes.
They include John Kerry, Madeleine Albright, Condoleezza Rice and former CIA directors Michael Hayden and Michael Morrell.
A coalition led by some of the world's biggest tech firms is also taking on the ban, with Elon Musk's Tesla and SpaceX the latest to add their names to a list of 30 companies including Apple, Facebook, Google, Microsoft and Twitter.
Mr Trump has continued to defend his executive order, saying: "Radical Islamic terrorists are determined to strike our homeland as they did on 9/11.
"We need strong programmes for people who love our country."
Meanwhile, the President has accused the media of deliberately minimising coverage of the threat posed by Islamic State.
A bizarre list of 78 terror attacks has been released by the White House, with the administration claiming "most" of them did not get sufficient media attention.
Among the incidents included on the hastily written list was the Paris attacks of November 2015 and the San Bernardino shootings of December 2015, both of which received widespread attention and in-depth reporting.
Less high-profile incidents in which nobody was killed were also on the list.
White House spokesman Sean Spicer said: "Like a protest gets blown out of the water, and yet an attack or a foiled attack doesn't necessarily get the same coverage."
Additional reporting by IRN ...