American Express heads to court to defend itself in an antitrust lawsuit brought on it by the U.S. Justice Department. The government agency charges Amex with impeding competition with its restrictions on merchants. The credit card company, which charges some of the highest processing fees, bans merchants from offering incentives to customers who pay in cash or with lower-charging credit cards. The lawsuit stems from a 2010 case whereby the Justice Department and 17 states, including Michigan, Ohio and Texas, sued Amex, Visa and MasterCard. However, Visa and MasterCard have since settled the charges against them.