Arizona Attorney General Mark Brnovich on Monday issued a legal opinion that determines that the ongoing crisis at the southern border is an "invasion" under the Constitution – a move he says gives the state the power to take additional measures to defend itself.

In the opinion, Brnovich says that the definition of "invasion" contained under the U.S. Constitution is not limited to hostile foreign states, and can include "hostile non-state actors." 

HARRIS SAYS EFFECTS OF BIDEN MIGRATION POLICY WON'T BE SEEN ‘OVERNIGHT,’ AS BORDER CRISIS RAGE

"The violence and lawlessness at the border caused by transnational cartels and gangs satisfies the definition of an ‘invasion’ under the U.S. Constitution, and Arizona therefore has the power to defend itself from this invasion under the Governor’s authority as Commander-in-Chief," Brnovich writes. "An actual invasion permits the State to engage in defensive actions within its own territory at or near its border." 

The opinion comes after Republican state lawmakers and former Trump officials -- including former Office of Management and Budget (OMB) Director Russ Vought and former acting deputy DHS Secretary Ken Cuccinelli, both now at the Center for Renewing America -- urged Gov. Doug Ducey to use war powers to repel the enormous number of migrants that have hit Arizona’s border with Mexico in the last year. It would in theory allow Arizona’s police or National Guard to remove illegal immigrants to Mexico themselves.
 

A pair of migrant families from Brazil pass through a gap in the border wall to reach the United States after crossing from Mexico in Yuma, Ariz., Thursday, June 10, 2021, to seek asylum. The families are part of an influx of asylum-seekers entering the U.S. in the Yuma area from South America and other continents. (AP Photo/Eugene Garcia)

They have pointed to language in Article I of the Constitution, which allows for States to "engage in War" when it has been "actually invaded, or in such imminent Danger as will not admit of delay" without the approval of Congress. They also note Article IV says the U.S. "shall protest each [state] against invasion."

There were more than 1.7 million migrant apprehensions in FY 2021, and the numbers remained high into December, where there were 178.840 encounters at the border, amid fears that the crisis will likely continue well into 2022 at least. Arizona’s Yuma Sector has been particularly overwhelmed by the surge in migrants.

"The on-the-ground violence and lawlessness at Arizona’s border caused by cartels and gangs is extensive, well-documented, and persistent. It can satisfy the definition of "actually invaded" and "invasion" under the U.S. Constitution," Brnovich’s opinion says.

While the Biden administration has focused on an explanation of the crisis that centers on "root causes" like violence and corruption in Central America, Republicans at state and national level have blamed the Biden administration’s rolling back of Trump-era border policies and of having left states to fend for themselves.

"No State should be put in the position that Arizona and other border states have been put in through the federal government’s recent actions," Brnovich writes.

He goes on to argue that "invasion" does not necessarily require foreign states and can instead include hostile foreign actors -- including transnational gangs and cartels bringing violence and drugs like fentanyl to the border.

ARIZONA GOV. DUCEY SAYS BIDEN'S BORDER POLICY SERVES AS ‘MARKETING ARM’ OF MEXICAN CARTELS 

"Furthermore, the commonly understood meaning at the time of the word "invade" covers the activities of the transnational cartels and gangs at the border—they enter Arizona "in [a] hostile manner"; they "enter as an enemy, with a view to ... plunder"; they "attack," "assail," and "assault"; and they "infringe," "encroach on," and "violate" Arizona," he said.

However, Brnovich notes that it will ultimately up to the governor of the state to make a determination whether the State is able to use its powers under the State Self-Defense Clause and that "only the Governor has the authority to establish the exact parameters for the exercise of the defensive use of force."

Cuccinelli told Fox News that it was a "big deal" for Brnovich to come to the conclusion he did.

"Now we call on Gov. Doug Ducey to use this very clear legal and constitutional authority to protect the people of Arizona from the invasion they're suffering through their southern border," he said.

"It's not enough for states like Texas, New Mexico, Arizona and California to complain about Joe Biden's failure to do his job, they have the authority to protect themselves," he said. "Only governors Abbot and Ducey have spoken about doing that. But here is confirmation that they have legal authority to take matters into their own hands and solve the problem, not just complain about it."

Ducey himself has been highly critical of the Biden administration’s border policies. In a recent interview with Fox News Digital, he said there was a link between rising crime and the influx of migrants into the U.S.

CLICK HERE TO GET THE FOX NEWS APP

"Well, of course, there's a link between criminals coming over the border and rising crime – of that, there's no doubt," he said. "We've got nearly two million people that we've apprehended at this time. So, border security is national security. The federal government is failing at that." 

In a statement in response to the opinion published on Monday, Ducey's office noted his deployment of the National Guard to the border and that he extended the border security mission for another year in August – while calling the amount of drugs and migrants coming across the border "unprecedented."

"DHS Secretary [Alejandro] Mayorkas admitted himself the border is the worst it’s been in over 20 years. He needs to be held accountable. This administration needs to be held accountable. They have totally failed to address this very real public safety and humanitarian crisis," Communications Director CJ Karamargin said.

"Arizona has and will continue to protect our communities with our National Guard, our Border Strike Force and in partnership with local law enforcement," Karamargin said. "For Attorney General Brnovich to imply the Guard is not on our border does them a serious disservice and shows that he fails to appreciate the commitment these men and women have to protecting Arizona."

Fox News' Danielle Wallace and The Associated Press contributed to this report.