What few people knew, including some of the recruited veterans themselves, was that Saudi Arabia's government was largely paying for the effort, worth hundreds of thousands of dollars.
Despite a World War II-era US law requiring lobbyists to immediately reveal payments from foreign governments or political parties, some of the campaign's organisers failed to notify the Justice Department about the Saudi kingdom's role until months afterward, with no legal consequences.
The chief lobbyist for the Saudi Embassy in Washington said it encouraged its subcontractors to be as transparent as possible. But the campaign and the allegations surrounding it show what can happen when the often-murky world of lobbying intersects with emotive American issues like patriotism, protecting US troops and the memory of September 11.
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"If the purpose of the statute is to make a public record about how foreign sovereigns are spending money to influence US policy, it's not clear how the Justice Department's relatively lax enforcement of the statute furthers that goal," said Stephen Vladeck, a law professor and national security law expert at the University of Texas.
Congress voted overwhelmingly for the law in September, overriding a veto by US President Barack Obama in his final weeks in office. The law, known by the acronym JASTA, gives victims' families the right to sue any foreign country found to support a terrorist attack that kills US citizens on American soil.
While the bill mentioned no countries, its supporters acknowledged that it took direct aim at Saudi Arabia. Fifteen of the 19 September 11 hijackers were Saudis. The attacks masterminded by al-Qaeda's Saudi-born leader Osama bin Laden killed nearly 3,000 people in New York, Washington and Pennsylvania.