Our Westie Is 8 Mos Old. He Takes Every Opport. To Run Off. He Waits For The Kids To Open Door And He Splits.?

If our kids open front door he is gone. Now we trained him to come and if we are in the house he comes right away and if we are in the backyard e comes right away, but if he is in the front yard he knows he isnt limited by a fence and he will not respond but run farther and faster. we have decided to quit chasing him and he will just stay gone. Help husband is starting to not like this dog.