The CBP does not revoke visas, the Department of State does. However, itu2019s part of a CBP officeru2019s job to find out whether you are the person on the visa, the visa is genuine & valid, and that you have not committed anything that makes you inadmissible into USA. As far as I know there is no procedure requiring the CBP to confirm your employment with the employer, but they are not prohibited from doing so.Employment verification is usually an established process in US companies, handled by their Human Resource department. The CBP is not the only party with potential interest in your employment status, banks and other prospective employers sometimes request this information as well. Itu2019s typically handled through mail correspondence, so it can take days. As such, itu2019s impractical for the CBP to verify employment, unless they are really suspicious of you, and theyu2019re willing to detain you for days while getting everything checked. Yes, they can detain you for days without a formal charge.