Using a unique data set merging micro-store level data with grocery markets data, this article provides an empirical analysis of a legislation that had the same effect as allowing industry-wide price floors. It shows that, after the introduction of the legislation, the link between retail prices and market concentration has significantly been weakened. Price dispersion has dropped for branded products more than for store brands and price convergence appears to have taken place across stores. These results are consistent with recent theories on the anti-competitive effects of resale price maintenance in markets with interlocking relationships.