Counter

[Avodroc13]

If someone casts a spell and I play {Render Silent} can they {Cancel} it?

[Ekann1]

Yes. Render silent's effect of not letting them cast spells only happens after it resolves and counters something else. Just like you had the opportunity to respond to someone and counter their spell with render silent,  they have the opportunity to respond to render silent and counter it with cancel.