I have encountered the noun phrase "such plea" in a lot of legal texts. Examples:
In federal courts, such plea may be accepted as long as there is evidence that the defendant is actually guilty. (source)
A defendant who has entered a plea of not guilty to an indictment may as a matter of right withdraw such plea at any time ... (source)
...to withdraw such plea, and in such event the entire indictment, as it existed at the time of such plea, is restored. (source)
This noun phrase strikes me as strange and ungrammatical, because as confirmed by dictionaries "plea" is a count noun. I would say "such a plea". Lawyer jargon?
I think it's safe to add a number of similar examples:
- such waiver shall only be effective during the Waiver Period