There are a lot of things that are totally OK to do for your wedding. You can make it an hors d'oeuvres-only event instead of a seated dinner reception or you can impose a formal dress code. But in order to pull these requests off, you need to politely communicate your vision on your wedding invites.
There are plenty of options out there to make your wedding specifics clear — just make sure to do your research to check and see what the standard wording is. For example, if you're trying to request that your guests dress formally, a small "Black Tie Attire Requested" along the bottom of your invite should do the trick.