WASHINGTON (Reuters) -Mergers in markets where there are a few big players will receive tougher scrutiny under guidelines that were finalized on Monday and released by the Justice Department, which works with the Federal Trade Commission to enforce antitrust law. The department said the new merger guidelines are aimed at encouraging fair, open and competitive markets. "These finalized guidelines provide transparency into how the Justice Department is protecting the American people from the ways in which unlawful, anticompetitive practices manifest themselves in our modern economy," Attorney General Merrick Garland said in a statement.