Waht's the best way to valide unique validation according to an attribute in a table

I'm using Laravel 5.1 , I've a model Customer which has many Vehicles. I set validations for Vehicle model like this :

public static $Rules = array(
    'code' => 'required|unique:vehicles', 
    'registernumber' => 'required|unique:vehicles'                       
);

Till now, all is fine : I can't insert two vehicles with the same code or registernumber.
What I want to do is :
Can I set a custom validation which allows me to insert unique code or registernumber value just for a given CustumerID ?

Example :

Customer1 :
Vehicle1: code1, registernumber1
Vehicle2: code2, registernumber2

  (Here I can't insert for example two codes having 'code1' value with Customer1)

Customer2 :
Vehicle1: code1, registernumber1
Vehicle2: code5, registernumber5

  (Here I can't insert for example two registernumbers having 'registernumber5' value with Customer2)

Any idea please ?

via Chebli Mohamed