Opponents are suing to end a federal program that could potentially give nearly half a million immigrants without legal status who are married to U.S. citizens a path to citizenship.Sixteen Republican-led states filed suit Friday to halt the program launched by President Joe Biden in June, saying in court filings that the Biden administration bypassed Congress to create a pathway to citizenship for “blatant political purposes.”Under the policy, which started taking applications Monday, many spouses without legal status can apply for something called “parole in place,” offering permission to stay in the U.S., apply for a green card and eventually get on a path to citizenship.But the program has been particularly contentious in an election year where immigration is one of the biggest issues, with many Republicans attacking the policy and contending it is essentially a form of amnesty for people who broke the law.To be eligible, immigrants must have lived continuously in the U.S. for at least 10 years, not pose a security threat or have a disqualifying criminal history, and have been married to a citizen by June 17 — the day before the program was announced.They must pay a $580 fee to apply and fill out a lengthy application, including an explanation of why they deserve humanitarian parole and a long list of supporting documents proving how long they have been in the country.They apply to the Department of Homeland Security, and if approved, have three years to seek permanent residency. During that period, they can get work authorization.The administration estimates about 500,000 people could be eligible, plus about 50,000 of their children.Before this program, it was complicated for people who were in the U.S. illegally to get a green card after marrying an American citizen. They can be required to return to their home country — often for years — and they always face the risk they may not be allowed back in.