Donald Trump has spent the last days before a crucial midterm election hammering down a singular point: his administration will do anything it takes to secure the US-Mexico border.

The president’s policy ideas, often arriving off the cuff during media interviews or from behind the White House podium, have ranged from sending up to 15,000 active duty military troops to the region — despite the administration’s apparent knowledge of a virtually non-existent threat level — to building “massive tent cities” to house detained migrants.

There’s just one question: Is any of this legal?

For starters, there are several claims the president has made in recent days that can be immediately refuted: no, he cannot upend the US Constitution and remove birthright citizenship from the 14th Amendment with an executive order.

Despite proposing the military treats rocks potentially thrown at them by migrants as “firearms” during a Thursday speech, it is not likely any active duty troops will fire at unarmed travellers.

Nor is it likely a massive influx of migrants will arrive imminently at the border, as the four caravans drawing national attention this election season are thousands of miles away — and the vast majority of migrants have been peaceful throughout their journeys.

Donald Trump says stone-throwing migrants could be shot by US military

Mark Hertling, a retired Army general, wrote on Twitter after Trump’s speech that no military officer would allow a soldier to shoot an individual throwing a rock. “It would be an unlawful order,” he wrote, citing the Law of Land Warfare.

However, other aspects of the president’s plans for overhauling current asylum guidelines remain legally questionable.

Mr Trump said Thursday that, under his order, any migrants who do enter the country would be housed in sprawling tent cities he plans to build while their cases are processed.

“We’re going to catch, we’re not going to release,” he said.

Under current protocol, many asylum seekers are released while their cases make their way through backlogged courts — a process that can take years.

“He’s really trying to scare the American public into thinking these are thousands of dangerous thugs,” said Greg Chen, of the American Immigration Lawyers Association. “It’s a classic strategy that goes back to 19th century nativist thinking.”

The president and other administration officials have long said those seeking asylum should come through legal ports of entry. But many migrants are unaware of that guidance, and official border crossings have grown increasingly clogged.

Immigration officials have turned away asylum-seekers at border crossings because of overcrowding, telling them to return at a later date. Meanwhile, backlogs have become especially bad in recent months at crossings in California, Arizona and Texas, with people generally waiting five weeks to try to claim asylum at San Diego’s main crossing and sleeping out in the open for days at a time.

Honduran migrant caravan heads to the US Show all 20 1 /20 Honduran migrant caravan heads to the US Honduran migrant caravan heads to the US The caravan heads towards the US as they leave Arriaga in southern Mexico AFP/Getty Honduran migrant caravan heads to the US Honduran migrants rest in a basketball pitch in San Pedro Tapanatepec, southern Mexico AFP/Getty Honduran migrant caravan heads to the US The caravan heads towards the US as they leave Arriaga in southern Mexico AFP/Getty Honduran migrant caravan heads to the US A truck carrying migrants departs from Mapastepec, Mexico EPA Honduran migrant caravan heads to the US The caravan heads through Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US Migrants cross the Suchiate River in Tecun Uma, Guatemala EPA Honduran migrant caravan heads to the US Migrants rest in Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US Migrants strike the border fence between Tecun Uman, Guatemala and Hidalgo, Mexico AFP/Getty Honduran migrant caravan heads to the US Guatemalan soldiers stand guard at the Guatemala-Mexico border as the Caravan arrives EPA Honduran migrant caravan heads to the US Migrants bathe in a river in Pijijapan AP Honduran migrant caravan heads to the US Washing clothes in a river near Pijijiapan, Mexico AFP/Getty Honduran migrant caravan heads to the US Walking in Mapastepec, Mexico EPA Honduran migrant caravan heads to the US A truck carries migrants in Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US The caravan passes through Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US The main square of Pijijiapan, Mexico AFP/Getty Honduran migrant caravan heads to the US Migrants walk on the road from Usumatlan to Guatemala City AFP/Getty Honduran migrant caravan heads to the US Migrants hang on to the back of a truck in Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US Migrant woman and child in Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US A truck carries migrants in Mapastepec, Mexico AFP/Getty Honduran migrant caravan heads to the US Migrants rest in Mapastepec, Mexico AFP/Getty

Migrants who cross illegally are generally arrested and often seek asylum or some other form of protection.

Claims have spiked in recent years, and there is currently a backlog of more than 800,000 cases pending in immigration court.

Administration officials have railed against what they say are loopholes designed to encourage people, especially from Central America, to come to the US and claim asylum. Generally, only about 20 percent of applicants are approved.

Whether or not Mr Trump’s changes to asylum are legal or not depend on what form the policies take on once they’ve been prepared for implementation.

US immigration laws make clear that migrants seeking asylum may do so either at or between border crossings. But the president said he would limit that to official crossing points.

If the president signs an executive order either halting asylum processing between the nation’s ports of entry or demanding the rapid expansion of immigrant detention facilities across the border, the move would likely face immediate pushback and temporary injunctions from federal courts — as has happened during several other executive orders Mr Trump has attempted to sign into effect.

In one example, a court blocked his order that would effectively make it easier to fire federal employees. In another case, courts halted his travel restrictions on several Muslim-majority nations, before the administration later managed to push through a revised version of that ban.

The president’s latest actions would likely face that same legal uphill battle, along with numerous logistical obstacles as well.

Currently, the US doesn’t have space at the border to manage the large-scale detention of migrants, with most facilities at capacity.

What’s more, these broad plans could eventually face strong pushback from taxpayers, as thousands of active duty troops, massive border walls and tent cities all come with reportedly costly price tags that could soar well above $25bn. The vast majority of Americans support providing pathways to citizenship for undocumented immigrants currently residing in the country, as well as protection for children who have arrived with their families.

But it is not even clear the president intends on following through with any of these broad immigration ideas.

Critics said the Thursday speech seemed mostly designed to scare, with no specifics on what mechanisms Trump intended to use to push through his desired changes.

Administration officials have told the Associated Press that Trump intends to invoke the same authority he used to push through his controversial travel ban, but it’s not clear if that’s what he was doing with Thursday’s speech.

Support free-thinking journalism and attend Independent events

Mr Trump brought up immigration issues several times during a political rally Thursday night in Columbia, Missouri. He railed against “birth tourism,” where mothers from abroad travel to America to have babies so they will automatically be US citizens. And he denounced “chain migration,” where these new citizens then bring in their extended families into the country.

“You come into the country — you’re like two months old ... and you’re gonna bring ‘em all — your aunts and uncles and grandfathers and lots of people,” he said.