RoleService methods persisting Limitations also validate them using:

\eZ\Publish\SPI\Limitation\Type::validate()

Right now for invalid Limitations InvalidArgumentException is thrown, but a new exception (LimitationValidationException) should be defined through which these errors could be accessed, similar to https://github.com/ezsystems/ezpublish-kernel/blob/master/eZ/Publish/Core/Base/Exceptions/ContentFieldValidationException.php.

Also some methods that persist and validate Policy do not hint the exception thrown. This should be documented in PHPDoc and maybe also similar exception (PolicyValidationException?) should be considered.