The short answer is that is the correct grammatical choice.
Therefore, you would never say someone is "hardly free" to mean they are "not free." is it can hardly or cant hardly free
In fact, the Chicago Manual of Style, a widely respected grammar guide, notes that "can't hardly" is a common colloquialism that's often used in informal writing. However, it also recommends using "can hardly" in formal writing to avoid potential ambiguity. The short answer is that is the correct grammatical choice
Think of hardly as a tiny negative anchor. If you already have can’t (a big negative ship), adding hardly makes the sentence sink logically. the Chicago Manual of Style