I looked how Validation object is created. If instantiated directly it accepts a config. The trouble with this option is, __construct also requires some other things when used like this. Besides that, it just feels wrong to use these core classes like that in a framework like CodeIgniter, where services are the way to go. I wish validation class had a setter for manipulating protected properties like validation classes it has loaded upon instantiation. It has not got one for now. Another way is through extending the Validation class in the module and loading an extended config from the module. However, this also feels wrong. There should be no need for extending the class just to add a custom validation method. I wish registrars worked as advertised, because the simplest and the best method would be a quick modification to the App/Config/Validation.php file. As the last resort one can turn to add Class::validationMethod as a validation rule + add error message for the rule with the validation method used being Class::validationMethod, that's how I used to do it in CI3 and Kohana. It works, but having a validation method like 'Class::validationMethod' rather than 'validationMethod' looks ugly. Due to lack of better options I can live with this ugliness though. Finally, my custom method is for a captcha image. In this case some preloaded method can be used to do validation on user input. However, I'm pretty sure, sooner or later I'll run into something I won't be able to validate without a custom method in a module. As mentioned above, it would be really useful if the validation object had methods for manipulating loaded rules and possibly also templates. Hopefully, in some newer version. Thx for the advice and devoted time. Highly appreciated.