Reassignment to a vacant position is considered a reasonable accommodation for an employee's disability under the ADA.  What this means is that if, as a result of a disability covered by or within meaning of the ADA and/or its Kentucky state law counterpart, an employee requires an accommodation, a reasonable accommodation may be reassignment to a vacant position for which the employee is qualified to perform.  

One key point right off the bat is that the position actually be vacant; an employer is not required to create a vacancy.

Another key point is that the reassignment must not present an undue hardship on the employer. An accommodation is not reasonable if it creates or imposes an undue hardship on the employer. A change in the way things are done is one thing but an undue hardship is another.

According to the EEOC, the employee with the disability does not need to be the best qualified for the vacant position in order for the reassignment to be proper.  The idea is that we want to keep people employed and working notwithstanding any disability that they may have and, as long as they are properly qualified, the ADA aims to make sure that happens.

The relevant vacant positions are not necessarily limited to the employee's division, branch or department or other limiting and identifying entity.  According to the EEOC, the duty of reasonable accommodation can include assignment to any vacant position for which the employee with the disability is properly qualified. Again according to the EEOC, an employer's policy against transferring or reassigning employees from one division or department to another must give way to the duty of reasonable accommodation that the ADA creates and imposes.

The final point is that these are rules, but they are pretty general rules.  Questions about reasonable accommodation to an employee and undue hardship vary from situtation to situation and turn ultimately on the particular facts of the specific case.