"you need not / change your trade; I'll be your tapster still. / Courage!" :
When Mistress Overdone fears losing her source of income, Pompey faithfully encourages her that her trade will survive despite the law. He reiterates this conviction in 2.1 in a discussion with Escalus. He tries to explain to Escalus that for the poor levels of society, the "base" trades of the underworld are their only means of survival. "Truly, sir, I am a poor fellow that would live", he explains simply (2.1.222). "How would you live, Pompey? By being a bawd? What do you think of the trade, Pompey? Is it a lawful trade?" Escalus responds, seeking for Pompey to consider the morality of the trade. But Pompey just responds logically, "If the law would allow it, sir", demonstrating that he finds nothing wrong with the trade except for the authorities' restriction on it.
Later in the conversation, he tries to explain to Escalus that the laws against fornication, adultery, and prostitution are useless because the sexual desires of the citizens will naturally propel these actions regardless. "If you head and hang all that offend that way but for ten year together, you'll be glad to give out a commission for more heads. If this law hold in Vienna ten year, I'll rent the fairest house in it after threepence a bay. If you live to see this come to pass, say Pompey told you so" (2.1.237-41). This is precisely why Pompey tells Overdone she "need not change her trade". It is not legislation that will establish whether Mistress Overdone will prevail; instead, Pompey believes, "the flesh and fortune shall better determine" (2.1.251)