José A. Cabranes, a judge on the U.S. Court of Appeals for the 2nd Circuit, is the author of "Citizenship and the American Empire," a legislative history of the U.S. citizenship of the Puerto Rican people. Félix López is the former regional director of the Puerto Rico Federal Affairs Administration in New York.

In the wake of Hurricane Maria, a vast internal migration of U.S. citizens is likely in the months ahead, as tens of thousands of Puerto Ricans, possibly 1 million or more over time, choose to move to the U.S. mainland. If this migration occurs, it will be an additional, slow-motion disaster inflicted on an island that can ill afford to lose any more of its best and brightest. As the federal government considers how robustly to respond to Maria, it should keep in mind the need to avoid compounding the already catastrophic damage the island has suffered.

The storm destroyed Puerto Rico's fragile power grid. Estimates suggest that power may not be fully restored for many months. If this is so, Puerto Rico's already struggling economy will be crippled for years, trapping more than 3 million of our fellow citizens in an economic nightmare. Maria damaged dams, bridges and roads, demolished homes and businesses, and wiped out much of Puerto Rico's admired greenery.

Puerto Rico, of course, is hardly alone in suffering hurricane damage, and the federal government must continue its recovery programs in Texas and Florida. But as an isolated island with no power and little communication, it is experiencing a dire crisis. Should basic services fail to return soon, social and economic disorder will prompt willing and able Puerto Ricans to seek temporary, or possibly permanent, refuge among friends and relatives already living on the mainland. They are likely to choose warm-weather localities that are familiar, hospitable and welcoming, such as Texas and Florida, currently confronting their own natural-disaster recovery. About 1 million Puerto Ricans already live in the Sunshine State, and Puerto Ricans are projected to soon pass Cubans as the largest group of Latinos in the state.

Any such migration can only accelerate and deepen the social and economic crisis in Puerto Rico. This is because it will consist in large measure of the educated and professional middle classes — those who came to maturity in the past five decades as a result of the island's justly celebrated program of economic development and modernization. Large numbers of Puerto Rican medical doctors, engineers and teachers have already left the financially strapped island for Texas, Florida and other states.

Until the 1940s, Puerto Rico was a desperately poor agrarian society, an embarrassment to an American empire whose armed forces had seized the island from Spain during the Spanish- ­American War of 1898, promising Puerto Ricans "the advantages and blessings of our enlightened civilization." By 1917, the people of Puerto Rico had become U.S. citizens with an elected bicameral legislature and a governor appointed by the president. Puerto Ricans have elected their own governor since 1948, and their 1952 commonwealth constitution resembles in most respects the basic law of an American state, except that Puerto Rico's more than 3 million American citizens have no voting representation in Congress.

The Puerto Rican constitution represents the faith that Puerto Ricans placed in the American project. In the 1950s and '60s — when many of its Spanish- ­speaking neighbors flirted with or turned to Marxism — Puerto Rico embraced democratic self-government, tax and labor policies specially tailored by a sympathetic Congress, and free-market economics. It became an exemplar of how a colonial people under the American flag could lift itself from poverty without communist depredations.

Of course, all Puerto Ricans are deeply conscious that the island's subordinate political status has made them unusual U.S. citizens. Nonetheless, Puerto Ricans know that they are entitled to the protection of the United States and that they are free to move to the continental United States and — in the words of a unanimous decision by the Supreme Court — become "residents of any State there to enjoy every right of any other citizen of the United States, civil, social and political."

The freedom to travel is a fundamental constitutional right, and citizens in Puerto Rico are free to exercise it. But as lawmakers consider a new round of disaster relief funding next month, they should keep in mind: The damage of a hurricane can be repaired only after the fact. The damage of large outward migration can be prevented, at least in part, by assuring Puerto Ricans that they will have a promising future at home.