No!! They must have a warrant if your charges are dismissed. They probably lost your finger prints and want them for their data base. You however are not obliged to comply unless a judge grants them a warrant. By the way probable cause does not apply in this case they must have a warrant as this is considered a search and as such you have the right to refuse. The only way they could require you to give fingerprints is under special circumstances. If those applied you should know it.
They can do whatever they want. They take your finger prints to usually do a live scan. If u were convicted or not they still need to make sure your not wanted somewere else in the world before cutting ties with you. It's there job
Inform the lawyer that helped to get your case dismissed, he/she can advise you best on what to do since he knows all the particulars involving the case..I have heard of cases being re-opened because of new evidence turning up so if I were you I would def contact a lawyer..good luck.