Trying to send command for object without authority?

Hey everyone!

I've been slaving away for weeks on a card game project I decided to make as a learning experience for Unity. Took a while because I'm extremely new to Unity and the whole networking concept, which brings me to the problem here.

Each player gets auto-created through the Network Manager script, as a prefab which contains both a Network Identity (tried with and without local player authority) and a script, containing parts of the following code:

    void LateUpdate () 
     {
         if (isClient && !isServer) {
             CmdReduceDeck ();
         }
     }
     [Command]
     void CmdReduceDeck()
     {
         print ("Executed command successfully");
     }

Now, whenever I launch two instances of the game, and the second player (not the host/server) connects, I get " Trying to send command for object without authority" in the client's debug log and, as expected, nothing on the server's end. What am I doing wrong?