Laws to Suppress

Spacetime, the Group Leader of The Edge of Knowledge group at MySpace.com has the following quotation on his profile page:

Laws to suppress tend to strengthen what they would prohibit. This is the fine point on which all the legal professions of history have based their job security.
–Bene Gesserit Coda (Dune)

To what degree is this true and to what degree is this an exaggeration of one inevitable aspect of lawmaking? Why is this so?