WASHINGTON — The House passed a bill yesterday that would make all private contractors working in Iraq and other combat zones subject to prosecution by American courts. It was the first major legislation of its kind to pass since a deadly shooting last month involving Blackwater employees.

Democrats called the 389–30 vote an indictment of the shooting incident there that left at least 13 Iraqis dead. Senate Democratic leaders said they planned to follow suit with similar legislation and send a bill to President Bush as soon as possible.

“There is simply no excuse for the de facto legal immunity for tens of thousands of individuals working in countries” on behalf of America, Rep. Sheila Jackson-Lee, a Democrat of Texas, said.

The FBI arrived in Baghdad yesterday to investigate the September 16 shooting, although administration officials acknowledge they are unsure whether American courts would have jurisdiction in the case or others like it.

In a separate incident, a drunk Blackwater employee left a Christmas eve party in Baghdad and fatally shot the guard of one of Iraq’s vice presidents. That contractor was fired, fined, and returned home to America, but no charges have been filed.

The current law, called the Military Extraterritorial Jurisdiction Act, covers personnel supporting the mission of Defense Department operations overseas. But because Blackwater’s primary mission is to protect State Department officials, defense lawyers would likely argue that the law doesn’t apply.

At the same time, all American contractors are immune from prosecution by Iraqi courts.

The bill’s passage came on the same day that a government minister told the Associated Press that the official Iraqi investigation said Blackwater security guards involved in the September incident face trial in Iraqi courts and the company should pay compensation to the victims.

The White House and congressional Republicans said they support the intent of the bill, but thought it was drafted poorly.

In a statement issued Wednesday, the White House said the bill would have “unintended and intolerable consequences for crucial and necessary national security activities and operations.” The statement did not explain further or give examples on how the bill would affect national security.

The White House referred questions to the Justice Department, which declined to comment.

Prior to passage, the House voted 342–75 to ensure the legislation would not affect intelligence operations.

Rep. Chris Shays, a Republican of Connecticut, accused Democrats of rushing the bill through Congress in a partisan bid to criticize the Bush administration’s handling of the war.

“It is amazing to me the number of men in Blackwater that have lost their lives and we never hear it on the other side of the aisle,” Mr. Shays said. “Blackwater is evil. That’s the way it appears in all the dialogue.”

Rep. David Price, who sponsored the bill, said the White House’s objections were unfounded and “should infuriate anyone who believes in the rule of law.”

Blackwater founder Erik Prince told a House panel Tuesday that he supports expanding the law.

“Beyond firing him for breaking the rules, withholding any funds we can, we can’t flog him,” Mr. Prince said of the intoxicated Blackwater guard.