Innos can't delay rounds. It is the T's job to kill them. Camping isn't allowed before overtime but other than that there is no way for a T to delay a round.
If someone is delaying as a T though and are refusing to take action even after you gave them sufficient warning you can slay them. Don't go overboard with this but if it's really someone like you describe delaying over multiple rounds as a T you are free to issue them an autoslay.