So you are still using the propel - the blazing fast php orm but you want to narrow/scope your result by a complex/not daily condition?
No problem you can use a subquery and put it to the where condition area.
The example is shipped with a validator collection which contains all needed validator items. It would definitely make more sense, if you would name that validator collection more specific like "IsValidTableForGermany" (or "IsValidUserName" if you want to switch context). All validator items need a injected table example class. Since the requirement component is dealing with automatically injection, you don't have to take care about this :-).
As you can see in the example class, all you have to do is to inject the item you want to validate and call "isMet()". The example itself creates a bunch of tables by choosing random properties.
What are the benefits of using the requirement component also for validation? Reusable and simple testable validator items and a endless flexibility of item combination by using the power of existing and and or condition.