It is a very long process for people interested in the USA to actually get in. They do a lot of searches on you and they also make you do a lot of forms. It is also a lot of money to try to get into the United States. Usually people that follow the law of the United States go to the U.S. Citizenship and Immigration officials to qualify and receive consent to enter the US. When that person gets approved, they get a permanent visa and can immigrate as a lawful permanent resident. They also receive a permanent resident card called a green card. This gives them the legal consent to live and work and attend in the USA. This card includes a lot of information about a person. It includes of course a persons name, their date of birth, picture, and fingerprint. People that have visas and green cards get into the USA for a specified amount of time. Immigrants must get a new permanent card every ten years or they are in jeopardy of getting deported. It’s a very long process which is why most people sneak into the US to get in. These people are known as illegal immigrants. It is a matter of chance and luck to get in. it is estimated about 50,000 get in every year legally. So the overall answer is  the law for getting in the US legally is having a permit.