The allusion to the WPA only further illustrates how awful Bob Ewell really is. He is so lazy that even the WPA (who was created for the purpose of people finding jobs and jump starting our economy again after the Depression) fired him because of his laziness. So Lee took it beyond just Maycomb, and showed the reader that even the state/national level wasn't happy with Bob or his way of life.
The allusion to the Ladies' Law is again pointed towards Bob and his treatment of Helen Robinson. He was so nasty that he would torment Tom's widowed wife. Link Deas protects her and threatens him with sticking him with "the Ladies' Law" which would put him in jail for some time. It was something the state of Alabama enforced at the time. No one was to speak inappropriately in front of or near women (who were thought of as delicate and impressionable, I suppose). They wanted to protect women from the harsh realities of life. This indicates that Bob was a harsh reality himself. He could be fined up to $200.00 and jailed, so that kept him from harassing Helen anymore.