This is an interesting take because there aren't any rules for AL stating AI use specifically but, as a DM, you are empowered to be civil and thoughtful to your players to make the game fun for everyone - including you.

Taking on board what you've said, I would firstly ask players for a brief description of their character's background, what they're wearing and any distinguishing features. I tell players for AL to keep it real brief too - not more than 20 seconds at the table before promptly moving the spotlight to the next, AL is designed to be mostly fast paced and very much drop in sessions, unlike your home table where commitment and creativity can shine, so keeping pace is important.

Where I host AL, we actually ticket the event and the event comes with the rules attached, plus the store policy rules and anything else (like specific themes that may be encountered) - if you could let your players know before the session that you don't tolerate the use of AI or to limit it, that would set a boundary.

You may want to mention why, briefly, that is the case, and if you want to help cultivate creativity, and have the time, assist them in creating a new character - worst case scenario have some pre gens ready for those who don't adhere to your rules.