Prevent Node Creation with Rules

The original teaser for this is kind of misleading. The general question: is it possible to prevent the creation of a node with Rules? Based on a condition, can you cancel the creation of that content? I guess an option would be a special purpose role, that has permission to create the content, which is added or removed by the rule.

I'm using Userpoints along with Ubercart to deal with purchases on a new site I am developing. The trick is that I want to do as much of the site logic as possible with the rules module, particularly as alot of the necessary modules for Userpoints are not D6 compliant yet. Turns out the Rule->Userpoints integration module doesn't do a whole bunch, yet, besides grants, looks like I'll need to work with the author and patch that, so I can check for userpoint totals.

In any case, this is a much more general question: is it possible to prevent the creation of a node with Rules? Eventually, I'll create a condition (might be just using the PHP filter, who knows) that will check if you have enough userpoints to create a certain type of content. Is there any action available that can prevent the creation of that content? If not a direct action, what kind of strategy can I follow to implement this functionality? I know I need two rules- one to prevent the creation of the node, and a second to charge userpoints when the node is created. The second is pretty easy. Any suggestions on the first? Thanks!