restrict query in callback

Hi,

I want to do some checks prior to some queries in the model.
In the $beforeUpdate and $beforeDelete callback I append the query by 

PHP Code:

$this->builder()->where('id', null); 


when the conditions are not met. (my ID's won't ever be NULL, resulting in an UPDATE or DELETE which won't work)

But this won't work on an insert.

I have a callback which determines whether the insert is valid, but I can't find a way to prevent the insert from happening when the right conditions are not met.
I have tried $this->builder()->resetQuery, but that still doesn't prevent the query from running...