Transferring Back/"Readmission"

<p>I transferred from one top 5 national university to another and am looking into transferring back for the start of the next term through my first institution's readmission process. The school states that it is "not obliged" to accept applications for readmission, but how selective are they? I withdrew from my first school in good standing with excellent grades and have both of those things at my current school, and I haven't had any disciplinary or financial issues. Is there any reason to think my previous institution would deny a request for readmission?</p>