To rein up

Rein \Rein\, v. t. [imp. & p. p. {Reined} (r?nd); p. pr. & vb.
   n. {Reining}.]
   1. To govern or direct with the reins; as, to rein a horse
      one way or another.
      [1913 Webster]

            He mounts and reins his horse.        --Chapman.
      [1913 Webster]

   2. To restrain; to control; to check.
      [1913 Webster]

            Being once chafed, he can not
            Be reined again to temperance.        --Shak.
      [1913 Webster]

   {To rein in} or {To rein up},
      (a) to check the speed of, or cause to stop, by drawing
          the reins. Hence,
      (a) to cause (a person) to slow down or cease some
          activity; -- to rein in is used commonly of superiors
          in a chain of command, ordering a subordinate to
          moderate or cease some activity deemed excessive.
          [1913 Webster +PJC]