Exactly five days after the spectacular march in Washington against Donald Trump's assumption of office, the 45th US President has cracked the whip. There are two facets to Wednesday's presidential decree to confront the issue of immigration in a country built by migrants.

Indeed, the population construct has been the striking feature of American history. The first item on the new agenda is to construct the Mexico Wall; the other is to impose a check at the immigration counters to entry from the seven — to begin with? — predominantly Muslim countries, notably Syria, Iraq, Iran, Libya. Sudan, Somalia, and Yemen. On closer reflection, he has targeted the volatile Afro-Arab bloc that has been in ferment for the past six years.

His policy on Mexico would appear to have hit the bumps at the threshold, however. Its President, Enrique Pena Nieto, has declined to visit the US to meet Trump next week… as expected by the White House. Furthermore, Mexico has refused to bear the cost of the Wall, conveying the message that it was presumptuous on the part of Trump to sign the order, and eventually forward the bill across the porous southern border in Tijuana.

Has homeland security floundered on the rock of reckless diplomacy? In the greater scheme of things, America could face a human rights crisis in the wake of the decidedly xenophobic immigration orders. The decision on the Wall, almost coinciding with the inaugural, and the withdrawal of funding to “sanctuary cities”, notably San Francisco and San Diego (bordering Tijuana), points to a long-term move to replace the so-called “catch and release” border policy with mandatory detention.

Arguably, the other compulsion to act with exceptionally urgent despatch was to emit a signal to those who had organised the massive anti-Trump march on 20 January, the day of his inaugural.

The President is now effectively at war with undocumented migrants inside the US and those who attempt to cross the southern border without paperwork.

Theoretically, the policy cannot perhaps be faulted. Yet the executive orders that envisage a dramatic reversal of immigration policy run counter to UN reservations and the opposition articulated by human rights groups. The in-house challenge therefore will be no less forbidding.

The order to erect a Wall across an additional 1,200 miles of the US southern border is bound to meet with stiff opposition when Congress is lobbied into funding the multibillion-dollar construction project. By the homeland security's own admission, the Wall will have limited effectiveness in deterring entry.

Misgivings that the proposal to withdraw funding to hundreds of sanctuary cities, which offer protection to undocumented migrants, will countenance legal opposition are not wholly unfounded. Trump has seemingly overlooked the repercussions in the flurry of executive action.