Health

• An applicant for citizenship or residency may be found inadmissible if they have not been properly vaccinated against common diseases such as polio, measles and mumps or if they have certain communicable diseases such as HIV/AIDS or tuberculosis.
  
  Known drug addicts or drug abusers are inadmissible as is anyone who has a mental or physical disorder which constitutes a threat to the health, safety or property of others. In some cases waivers may be available to aliens who can demonstrate that previous conditions are no longer an issue.
  
  

Character

• Anyone who has a significant criminal record including anyone with any convictions for drug trafficking or multiple convictions for any significant offense is generally inadmissible to the United States. For drug related offenses the U.S. may deny someone entry if U.S. officials believe that the person is involved in the drug trade, even if that person has never been convicted.
  
  In some cases, for certain offenses, or after a sufficient amount of time has passed, waivers may be granted on a case-by-case basis. Waivers may also be granted in cases where the individual has family members who are U.S. citizens. Under no circumstances is anyone who is seen to pose a risk to the health, safety and security of U.S. citizens, including those suspected of ties to terrorist organizations, granted immigrant status. Previous convictions for illegal entry into the U.S. will also usually result in the denial of admission.
  
  

Labor

• Any person seeking to enter the U.S. for the purpose of finding work must demonstrate that they have desirable education or skills and that there is a need for workers with those skills in the area in which they want to work. Additionally any person who, in the opinion of immigration officials, is likely to become a "public charge" by reason of age, health or financial status is inadmissible. Again waivers may be issued in certain cases generally at the request of family members who are U.S. citizens.
  
  

Sundry Criteria

• A number of other criteria are factored into citizenship. Special rules are available for individuals seeking to reunite with family members in the U.S., so long as those family members are U.S. citizens. This is especially true in the case of foreign nationals who are married to a U.S. citizen. Special rules also apply in the case of legal refugees admitted to the United States and those claiming asylum due to legitimate fear of persecution in their home country.