Among the provisions of the Raines [John Raines was a New York State politician] Law, as it became known, was a Sunday closing rule aimed at the saloons--a particularly potent measure because Sunday, when workers controlled their own time, had always been the saloonkeeper's best day. Conveniently, the law exempted many of its advocates from its strictures: because the preferred weekend dining and drinking places of the well-to-do were hotel restaurants, Raines crafted the measure to exclude any establishment that served meals and had at least ten bedrooms. As in the south, it was prohibition for the other guy, not for me.
But Raines failed to anticipate the resourcefulness of his law's targets. Instead of being weakened, the measure strengthened the saloon business immeasurably. In Brooklyn alone, where there had been thirteen hotels before the Raines Law, there were soon more than two thousand--virtually all of them saloons whose back rooms or upstairs spaces had been subdivided by the addition of flimsy walls, made accommodating by the provision of threadbare cots, and turned profitable by the new business they immediately attracted: prostitution. The requirement that these "hotels" offer food was solved with the invention of the "Raines sandwich," described by Jacob Riis [one of the 20th century's most annoying busybodies] as "consisting of two pieces of bread with a brick between . . . set out on the counter, in derision of the state law which forbids the serving of drinks without 'meals.'"
This is from the excellent Last Call: The Rise and Fall of Prohibition by Daniel Okrent.