Nevertheless, at a tumultuous mass meeting in the center of Rome, Pompey’s opponents were cowed into submission, the Lex Gabinia passed (illegally), and he was given his power. In the end, once he put to sea, it took less than three months to sweep the pirates from the entire Mediterranean. Even allowing for Pompey’s genius as a military strategist, the suspicion arises that if the pirates could be defeated so swiftly, they could hardly have been such a grievous threat in the first place.

But it was too late to raise such questions. By the oldest trick in the political book — the whipping up of a panic, in which any dissenting voice could be dismissed as “soft” or even “traitorous” — powers had been ceded by the people that would never be returned. Pompey stayed in the Middle East for six years, establishing puppet regimes throughout the region, and turning himself into the richest man in the empire.

Those of us who are not Americans can only look on in wonder at the similar ease with which the ancient rights and liberties of the individual are being surrendered in the United States in the wake of 9/11. The vote by the Senate on Thursday to suspend the right of habeas corpus for terrorism detainees, denying them their right to challenge their detention in court; the careful wording about torture, which forbids only the inducement of “serious” physical and mental suffering to obtain information; the admissibility of evidence obtained in the United States without a search warrant; the licensing of the president to declare a legal resident of the United States an enemy combatant — all this represents an historic shift in the balance of power between the citizen and the executive.

An intelligent, skeptical American would no doubt scoff at the thought that what has happened since 9/11 could presage the destruction of a centuries-old constitution; but then, I suppose, an intelligent, skeptical Roman in 68 B.C. might well have done the same.

In truth, however, the Lex Gabinia was the beginning of the end of the Roman republic. It set a precedent. Less than a decade later, Julius Caesar — the only man, according to Plutarch, who spoke out in favor of Pompey’s special command during the Senate debate — was awarded similar, extended military sovereignty in Gaul. Previously, the state, through the Senate, largely had direction of its armed forces; now the armed forces began to assume direction of the state.

It also brought a flood of money into an electoral system that had been designed for a simpler, non-imperial era. Caesar, like Pompey, with all the resources of Gaul at his disposal, became immensely wealthy, and used his treasure to fund his own political faction. Henceforth, the result of elections was determined largely by which candidate had the most money to bribe the electorate. In 49 B.C., the system collapsed completely, Caesar crossed the Rubicon — and the rest, as they say, is ancient history.

It may be that the Roman republic was doomed in any case. But the disproportionate reaction to the raid on Ostia unquestionably hastened the process, weakening the restraints on military adventurism and corrupting the political process. It was to be more than 1,800 years before anything remotely comparable to Rome’s democracy — imperfect though it was — rose again.

The Lex Gabinia was a classic illustration of the law of unintended consequences: it fatally subverted the institution it was supposed to protect. Let us hope that vote in the United States Senate does not have the same result.