After her latest blunder, is expecting Priti Patel to understand immigration rules really too much to ask?

If the goal with Brexit was to cut EU migration, that has already been achieved. Brexit has made itself redundant, as EU citizens deterred by the dangers of leaving the union choose to make their lives elsewhere

From its beginning, the Brexit campaign to leave the EU and "take back control" was based on a simple untruth: that EU freedom of movement is indeed completely free. This myth is so widespread, its fiction so tolerated, that few, if any, mainstream commentators have challenged it.

And yesterday, Priti Patel, the home secretary, sought to perpetuate that myth yet again in announcing the latest in a long line of false promises the Tories have offered to sell Brexit to the British people.

Patel promised that her party would, after Brexit, introduce a US-style visa scheme for any non-Brit visiting Britain. But while the idea of imposing a charge on foreigners might be popular with many Tory voters, the reality of that system would not be so welcome. For what Patel failed to mention was that a visa system would launch a visa price war with the EU – and one that would almost certainly increase the cost for Brits of travelling abroad.

The only way to unravel this myth weaving is to start with some basic facts.

First, movement within the EU is not unrestricted. As the European Court of Justice (ECJ) has affirmed, EU nationals cannot move willy nilly from one country to the next. Free movement is not a right to claim benefits from whichever EU member state is offering the best deal; if a person has no realistic prospects of work or study, there is nothing preventing any EU country from booting them out. In fact, the UK has already kicked out hundreds of EU citizens for violating free movement rights.

Apparently, expecting a home secretary to be familiar with the immigration rules she is managing is asking too much. Then again these rules have been in place since day one, so any ignorance is likely feigned.

Second, despite the assumptions of many politicians and voters, EU net migration continues to decline. If the goal with Brexit was to cut EU migration, that has already been achieved. Brexit has, in that sense, made itself redundant as EU citizens deterred by the dangers of leaving the union choose to make their lives elsewhere.

It's easy to see why so many believe the Conservatives are clueless about immigration. Not only do they peddle myths about immigration and ignore the Home Office's annual success in kicking EU citizens out, their "answers" to the problem are all halfhearted assertions about their ability to repatriate good idea on immigration from elsewhere – most of which are not very good at all.

The US-style visa system is one such example, and as I have said a UK version of the American Electronic System for Travel Authorization (ESTA) would be deeply unpopular. Another is the Australian-style points-based immigration system. The problem is that such a system already has existed for the UK, albeit only for non-EU citizens, for 10 years.

All of which begs the question: is this really the best the home secretary can do? Import an immigration system from deeply contested jurisdictions such as the US and Australia, raising the costs of foreign travel and doing nothing to dent record levels of non-EU migration, rather than create one that befits our history and culture?

Such a lack of originality, imagination and indeed pragmatism will only make a bad situation worse.

Thom Brooks is professor of law and government at Durham University