My favorite example of the restrictive/non-restrictive/ambiguous
adjective clause comes from a plank of the Republican platform in 1984.
I put the problem to my students this way:
 
 
     When the Republicans were putting their platform together
     in 1984, there was intensive fighting about which way one
     particular plank should be written.  Explain the difference
     in meaning between these two:  (Hint:  In those days, Jack
     Kemp and Newt Gingrich fought to use version B.)
 
     A.  Republicans oppose any attempts to increase taxes which
         would harm the recovery and reverse the trend to restoring
         control of the economy to individual Americans.
 
     B.  Republicans oppose any attempts to increase taxes, which
         would harm the recovery and refverse the trend to restoring
         control of the economy to individual Americans.
 
     Question:  With which wording can the Republican make BOTH of
                these statments?
 
                1.  "See, we told you we would not increase taxes!"
 
                2.  "See, we told you we might have to increase taxes."
 
 
     (Source:  "Rallying Round a Comma Cause," Time Magazine,
                August, 1984, p. 14.)