Why did the thieves and beggars drink to the English law?

In Chapter 17, Prince Edward has been lured into John Canty's clutches again. We are told in this chapter that Canty now calls himself John Hobbs. Meanwhile, the death of King Henry VIII, Edward's father, has been a great blow to Edward; the young prince now finds himself bereft of a father and is a prisoner to boot. Grieved beyond measure, he retires to the far end of the barn that he has been lured into and proceeds to brood. Eventually, he falls asleep.

He is soon rudely awakened by loud noises:

A bright fire was burning in the middle of the floor, at the other end of the barn; and around it, and lit weirdly up by the red glare, lolled and sprawled the motliest company of tattered gutter-scum and ruffians, of both sexes, he had ever read or dreamed of.  There were huge stalwart men, brown with exposure, long-haired, and clothed in fantastic rags; there were middle-sized youths, of truculent countenance, and similarly clad; there were blind mendicants, with patched or bandaged eyes; crippled ones, with wooden legs and crutches; diseased ones, with running sores peeping from ineffectual wrappings...

These are the thieves and beggars you mention above; they form part of an underground group of thieves that John Hobbs belongs to. They drink and talk raucously in the barn. Soon, a thief named Yokel, who was once a prosperous farmer, tells of his sad fate living under English law. Accordingly, his mother was a healer who was burned as a witch after one of her patients died. After his mother's death (she appeared to be the main breadwinner of the household), the farmer found himself and his little family begging for food.

Yokel relates that his family members were unmercifully lashed "through three towns" because it was a crime to beg in England. Undeterred, Yokel had continued begging for food for his children. Meanwhile, his wife died from the injuries caused by the lashes, and his children starved to death. Yokel himself was sent to the stocks and both his ears were cut off as punishment. Eventually, he was sold as a slave but has since run away from his owner. He asserts pitifully that he will be hung, courtesy of the 'wonderful' English law, when he is found.

So, when Yokel encourages his fellow thieves and beggars to drink to the English law, he is actually mocking and criticizing the oppressive character of the law. His sarcasm, in tandem with his sad story, serves to illuminate the true, cruel nature of English law. At his story, Prince Edward is so incensed that he shouts out that he will do away with the kind of law that will hang a poor man for running away from slavery. The thieves and beggars in turn mock Edward for his proud announcement; they don't really believe he is the son of Henry VIII. The chapter ends with Edward feeling very sorry that he ever tried to extend kindness to this rabble group of subjects.