The burden is upon the foreign national seeking entry to the United States to prove that they are admissible. In other words, there is nothing criminal, medical, or otherwise, that would prevent them from entering the United States. You can be found inadmissible to the United States by USCIS, CBP, and a US Consulate. If you have been found inadmissible to the United States, you cannot enter without a waiver of inadmissibility or a determination that the finding of inadmissibility was done in error. We discuss how to overcome a refusal under 212(a)(7)(A)(i)(I) here.