BRUSSELS — In a setback for the United States’ attempts to isolate Iran, a European Union court threw out sanctions Friday on seven Iranian companies, including four banks, rejecting arguments that they were acting as front companies to bypass the punitive measures.

The General Court in Brussels, the union’s second-highest tribunal, ruled that the bloc wrongly imposed sanctions against the Iranian companies as part of its efforts to stop Iran from developing nuclear weapons, a decision that immediately drew the ire of American officials.

The United States Treasury took the opposite tack on Friday, imposing restrictions on a network of six individuals and four businesses for links to oil sales.

“We are very disappointed by the court’s decision today,” a Treasury spokesman said in a statement. “The evidence linking these banks to Iran’s illicit nuclear activities is clear and strong, and no financial institution anywhere should allow these Iranian banks to transact with them.”