Republican governors have been sending more migrants released at the U.S. border with Mexico to Democratic strongholds, raising questions about their legal status, how they are lured on board buses and planes and the cost to taxpayers.

Florida’s Ron DeSantis flew about 50 Venezuelans last week to the small, upscale island of Martha’s Vineyard in Massachusetts. During the weekend, Texas’ Greg Abbott bused more migrants to Vice President Kamala Harris’ Washington home.

U.S. authorities are grappling with unusually large numbers of migrants crossing the border from Mexico amid rapidly changing demographics. The administration said Monday that people from Venezuela, Cuba and Nicaragua accounted for more than one of three migrants stopped at the border in August. Authorities stopped migrants 2.15 million times from October through August, the first time above 2 million during the government’s fiscal year.

Since April, Texas has bused about 8,000 migrants to Washington, 2,200 to New York and 300 to Chicago. Arizona bused more than 1,800 to Washington since May, while the city of El Paso, Texas, bused more than 1,100 to New York since Aug. 23.

Here are some questions and answers:

ARE MIGRANTS LEGALLY IN THE UNITED STATES?

Yes, temporarily. Tens of thousands of migrants who cross the border illegally from Mexico are released in the United States each month with notices to appear in immigration court to pursue asylum or on humanitarian parole with requirements to report regularly to immigration authorities. Migrants may seek asylum if they enter the country illegally under U.S. and international law, and U.S. authorities have broad authority to grant parole based on individual circumstances.

Migrants must keep a current address with authorities, who schedule appointments in a city with the nearest court or immigration office. They must apply separately for permission to work.

Last year, it took an average of nearly four years for asylum cases to be decided in immigration court, according to the Biden administration, leaving migrants in a legal purgatory that shields them from deportation. The backlog in immigration courts has mushroomed to more than 1.9 million cases, according to Syracuse University’s Transactional Records Access Clearinghouse.

To avoid massive overcrowding in detention facilities, the administration began releasing many migrants on humanitarian parole. The Border Patrol paroled nearly 250,000 migrants from August through June, including 40,151 in June, the latest figures released. In the previous seven months, it paroled only 11 migrants.

ARE THESE MIGRANTS KIDNAPPED?

Kidnapping is a high legal threshold, but migrants flown to Martha’s Vineyard say they were taken there on false pretenses. Migrants sign waivers that the transportation is free and voluntary.

DeSantis used a state program under which migrants deemed “unauthorized aliens” can be moved “from Florida,” though the governor has acknowledged the flights originated in Texas.

They stopped first in Florida, before going to Martha’s Vineyard, but DeSantis has not emphasized that. Instead, he maintains that the two flights were a legitimate use of funds because the migrants otherwise would have aimed to go to Florida, though he offered no evidence of that and did not say how migrants might have been vetted.

Migrants who boarded the flights told The Associated Press that a woman who approached them at a San Antonio shelter promised jobs and three months of housing in Washington, New York, Philadelphia and Boston.

On Monday, Javier Salazar, the sheriff of Bexar County, which includes San Antonio, opened an investigation into the flights, but the elected Democrat didn’t say what laws may have been broken. Other Democrats have urged the U.S. Justice Department to investigate, including California Gov. Gavin Newsom and U.S. Rep. Joaquin Castro, whose district includes San Antonio.

DOESN’T THE BIDEN ADMINISTRATION BUS AND FLY MIGRANTS AROUND THE COUNTRY?

Yes, but under different circumstances. Like earlier administrations, it transports migrants between detention facilities, often on their way to being removed from the country.

U.S. Immigration and Customs Enforcement had more than 4,800 domestic flights in the last year, including 434 in August, according to Witness to the Border, a group that criticizes U.S. enforcement. The top five destinations from March to August were: Alexandria, Louisiana; Laredo, Texas; Phoenix; and Harlingen and El Paso in Texas. ICE also buses many migrants.

The Department of Health and Human Services transports unaccompanied children to “sponsors,” who are often family, or child-only detention facilities.

DID ANYONE ASK FOR THIS?

Republican-led states say they are sending migrants to “sanctuary” cities that welcome immigrants. While the definition of a sanctuary city is slippery, a sudden influx of migrants can test attitudes and limits of generosity.

Chicago’s “Welcoming City Ordinance” prohibits asking people about their immigration status, denying services based on immigration status and disclosing information to federal immigration authorities.

New York limits cooperation with U.S. immigration authorities, partly by prohibiting police officers from participating in joint enforcement or by letting immigration agents work in city jails.

In Martha’s Vineyard, the six towns that make up the island south of Boston haven’t issued any “sanctuary” declarations.

The Center for Immigration Studies, which advocates for restrictions, keeps an extensive list of “sanctuary” jurisdictions, which, by its definition, limit cooperation with federal immigration authorities. They include Boston and seven other Massachusetts cities. None of the towns in Martha’s Vineyard are on the list.

WHO’S PAYING AND HOW MUCH?

Texas has committed billions of dollars to Abbott’s “Operation Lone Star,” an unprecedented move into border security that includes the bus trips, prosecuting border crossers for trespassing and massive presence of state troopers and National Guard.

The Florida Legislature allocated $12 million for its program for the current budget year.

The city of El Paso, which last week contracted a private bus company at a cost of up to $2 million, plans to seek reimbursement from the federal government.