The immigration laws include restrictions which prevent some people from obtaining permission to enter the United States. Each restriction is called an inadmissibility.
When a visa applicant has a criminal conviction abroad and the foreign law is equivalent to the US law, the conviction can create an inadmissibility and the applicant is inadmissible and can be refused a visa.
To illustrate how this works, let me tell you about the famous case of John Lennon.
John Lennon was convicted in the United Kingdom for possession of cannabis. Since possession of Cannabis is also illegal in the United States, John was denied admission as a permanent resident alien because his conviction in the United Kingdom was equivalent to a conviction in the US. John was inadmissible.
John had visited many lawyers and submitted many petitions, but his applications to live in the United States were denied, not only according to the rules of the immigration service but also to the rules of the federal courts.
One fine day John walked into the office of a colleague of mine in New York City, Leon Wildes. The lawyer asked John for a copy of the criminal process in the United Kingdom, and after the lawyer reviewed everything carefully, he noted that there was no ‘mens rea’ in the accusation.
Mens rea is important in criminal matters because it means that the accused person committed an act purposely and knowingly. In the United States you can not be convicted of possession of cannabis if you did know that you had possession of the cannabis.
In the United States, you cannot be convicted of a crime if you did not have mens rea.
John’s lawyer filed a new petition to forgive John. Leon said that the law in the United Kingdom was not equivalent to the law in the United States because the law in the united kingdom did not include mens rea.
Since the U.S. law could not restrict persons who were convicted of a crime without mens rea, John Lennon was granted permission to immigrate to the United States as the spouse of Yoko Ono, who was a permanent resident alien.
The story had a happy ending for the moment, but, as everyone knows, John was assassinated in front of his apartment at the Dakota residential building on the corner of West 72nd Street and Central Park West -- bringing John's story to a very unhappy ending.