Prevent User from Creating Pull Requests, but permit Issue creation and Comments

I expect that the answer to this is “No” but I feel like asking anyway.

I have a Repository in an Organization, and I would like to prevent certain users from being able to create Pull Requests. I would like to permit them to still create new Issues, and comment on Issues or existing Pull Requests – just not be able to create new PRs.

It seems that the permission model for GitHub is entirely binary – you’re either permitted ALL interaction, or blocked from ANY interaction.

Is there some setting I’m missing that allows more fine-grained control?