Republican hopeful Ben Carson has demanded that all visitors to America should be asked the purpose of their visit before they are allowed in.
The former neurosurgeon, interviewed by CNN, proposed the introduction of a system of "visas", which, unlike the credit card all Americans carry will be a piece of paper that gives foreigners a limited right to visit America.
A foreigner will be expected to obtain a "visa" before he travels here and will have to pay a fee to get one. The application will require him to provide information about himself and the reason for his visit, and if his application is refused, he won't get his fee back.
Carson's innovative idea was criticised by Hilary Clinton, who told the Huffington Post that a "visa" system would be unconstitutional and that if everybody who travelled to America required a visa, neither the founding fathers not even Christopher Columbus would have landed on the shores of what is now America.
The population of the United Kingdom reacted angrily to the idea of "visas" and within an hour, half a million Brits had signed an online petition demanding that Ben Carson be banned from ever visiting the U.K.