It is WAR!

That's IT Mr. Gopher!  You are no longer welcomed here.  I tried to let you live here, but you have not followed the rules.  You have continued to dig holes in the front lawn and that is just not acceptable!  You had 1 acre to choose from and you insisted on living on 200 SF that is my front lawn.  Not cool!

Here is your eviction notice: carbon monoxide.

Side note:  This first attempt to gas him failed. 

You may have won this battle, Mr. Gopher, but we will win the war!