Anyone inadmissible due to a criminal record, immigration violation, or certain medical issues. This includes DUI, assault, theft, drug charges, multiple convictions, or prior denial of entry. Even one DUI can cause refusal. Overstays, deportations, or communicable illnesses may also require a waiver. If you’ve ever been denied, flagged, or told you need one, you must apply. In short: if you have a record and want to cross legally, a waiver is the safe solution.