By Lawrence Hurley

WASHINGTON (Reuters) - Immigration advocates on Thursday mounted a long-shot effort to revive part of U.S. President Barack Obama's plan to shield millions of immigrants from deportation by filing a lawsuit challenging the national scope of a court order that blocked it.

With favorable court rulings, the lawyers filing the lawsuit say it has the long-term potential to unravel decisions that blocked Obama's November 2014 plan nationwide. The White House program, if it had been fully implemented, could have allowed up to four million people with no legal immigration status to obtain work authorization.

The lawsuit was filed in federal court in New York on behalf of Martin Batalla Vidal, 25, an immigrant from Mexico who has lived in the United States since he was seven and has benefited from the program.

He initially received a three-year work authorization, which has now been revoked due to a Texas judge's ruling in February 2015 that blocked Obama's plan. Texas and 25 other states had challenged it.

Vidal would still be eligible for a two-year work authorization under an earlier program, which has not been challenged and was not covered by the injunction.

Vidal's lawyers at the National Immigration Law Center say that if he wins, the ruling could have broad implications because it could help to eventually reinstate Obama's program for up to 60 percent of potential applicants in parts of the country not covered by the Texas ruling.

The Texas judge's ruling was upheld on appeal. On June 23, the Supreme Court deadlocked 4-4 on the case, leaving the appeals court decision in place.

The court is currently one justice short following the death of Justice Antonin Scalia in February. The Supreme Court is currently considering whether to rehear the case once it has a full complement of justices.

(Reporting by Lawrence Hurley; Editing by Alistair Bell)