The Imperial Ban was a form of outlawry, and much like other writs of outlawry, effectively stripped that person of the protection of the law, and made them subject to pursuit and punishment under Imperial law.

The most prominent example I can think of is Frederick V, Elector Palatine, who was stripped of his lands and titles following his acceptance of the Bohemian crown, and his later deposition--although I am not sure how much of that was the Imperial ban, and how much was the general charges of treason and insurrection he was slapped with. However, Frederick had his lands occupied, and his electoral title transfered to a different branch of the Wittelsbachs (the Dukes of Bavaria), and spent the rest of his life in exile.

Another example was the city of Donauwörth, which was placed under the Imperial Ban following the riots regarding the St. Marks Day parade. The charge in this case was a breach of the Imperial peace due to the city council's failure to control the rioters. In this case, the Duke of Bavaria was ordered to enforce the ban by occupying the city and punishing the councilors.

While I am not an expert in Holy Roman law, it would seem that the consequence of an Imperial ban--at least in the early modern, I make no representations about the medieval system--result in the subject of the ban losing much of their protection under Imperial law, and thus making them subject to being removed from power or otherwise punished.

Hopefully this answers your question, and feel free to ask any follow ups! I'll do my best to answer.