Bank of America cannot require some of its longtime customers to submit disputes to an arbitrator rather than a jury, a state appeals court ruled. The ruling by the 1st District Court of Appeal should apply equally to 12.4 million customers who had credit cards or checking accounts with the bank in June 1992, when the bank changed its rules, said James Sturdevant, lawyer for four credit card customers who filed the suit. The bank's previous contracts with those customers gave the bank the right to change the terms of their accounts. But the court said the bank had no authority to impose an arbitration clause without the customers' consent. The court did not say whether an arbitration clause would be valid if it was contained in any account opened by a customer after June 1992. "This is a very significant victory for consumers," Sturdevant said. "You have to agree to contract terms. You can't have somebody come in the middle of the night and try to slip something past you." He said the bank had 9 million checking account customers and 3.4 million credit card customers as of June 1992. The bank's lawyer, Seth Hufstedler, said the bank will have no comment until it studied the ruling. Shares of San Francisco-based Bank of America fell 38 cents to close at $58.13 on the New York Stock Exchange.