Hello there!
I’m afraid there is no feature in our plugins that allow you to blacklist a user. However, if you are using Community Events for visitors to submit events to your calendar, then you can require that someone signs into WordPress first before being allowed to submit an event — and, as a registered user on your site, you have the ability to restrict their access from there.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff