President Biden on Tuesday is announcing a large-scale immigration program that will offer legal status and a streamlined path to U.S. residency and citizenship to roughly half a million unauthorized immigrants married to American citizens.

The Department of Homeland Security policy will allow these immigrants to apply for work permits and deportation protections if they have lived in the U.S. for at least 10 years and meet other requirements, senior administration officials said during a call with reporters.

Perhaps most importantly, however, Mr. Biden’s move will unlock a path to permanent residency — colloquially known as a green card — and ultimately U.S. citizenship for many of the program’s beneficiaries. The policy, if upheld in court, would be the largest government program for undocumented immigrants since the Obama-era Deferred Action for Childhood Arrivals (DACA) initiative, which currently shields 528,000 so-called “DREAMers” who were brought to the U.S. as children from deportation.

Mr. Biden is slated to announce the measure at a White House event on Tuesday marking the 12th anniversary of DACA, alongside another move to make it easier for employers to sponsor “DREAMers” and other undocumented immigrants for work visas.

It’s the second time in one month that Mr. Biden has taken a sweeping —and legally risky— executive action on immigration. Earlier in June, he invoked a presidential power used frequently by former President Donald Trump to disqualify most migrants at the U.S.-Mexico border from asylum.

How Biden’s immigration plan would work

The Biden administration program for undocumented immigrants married to U.S. citizens would provide two key immigration benefits.

It will allow eligible applicants to work and live in the U.S. legally on a temporary basis under the immigration parole authority. The policy, known as Parole-in-Place, will also help these immigrants clear roadblocks in U.S. law that prevent them from getting permanent legal status without having to leave the country.

An immigrant who marries a U.S. citizen is generally eligible for a green card. But current federal law requires immigrants who entered the U.S. illegally to leave the country and re-enter legally to be eligible for a green card. Leaving the U.S. after living illegally in the country for certain periods of time can trigger a 10-year ban, leading many mixed-status families to not pursue this process.

The Biden administration’s policy would allow eligible immigrants to obtain a green card without having to leave the U.S. After 5 years of living in the U.S. as a green card holder, immigrants can apply for American citizenship.

Administration officials estimate that roughly 500,000 unauthorized immigrants with U.S. citizen spouses will qualify for the program. Applicants must have been legally married to their American citizen spouse by June 17. Those who are deemed to pose a threat to national security or public safety will not qualify.

The policy is also expected to benefit an estimated 50,000 immigrant children with a parent who is married to a U.S. citizen, officials said. Undocumented stepchildren of U.S. citizens —who must also leave the country to obtain green cards— will be eligible to apply for the parole process if they are under the age of 21.

A senior administration official said the government is planning to open the Parole-in-Place program to applications “by the end of summer.” The policy will almost certainly generate legal challenges, possibly from Republican-led states, which have sued the Biden administration over its immigration policies several times.

For over a decade, the U.S. government has overseen a more limited Parole-in-Place policy for unauthorized immigrants who are the immediate relatives of U.S. service members or veterans. In 2020, Congress affirmed that policy.

The State Department is also announcing on Tuesday a streamlined process for DACA recipients and other undocumented immigrants who have graduated from U.S. colleges to more easily obtain employment-based visas, such as H-1B visas for high-skilled workers.