WASHINGTON (Reuters) - Transgender students at U.S. public schools were left in legal limbo on Monday about whether a federal anti-discrimination law enables them to use the bathroom of their choice after the Supreme Court sidestepped a major ruling on the issue.

Student Gavin Grimm, who was barred from using the boys' bathroom at his local high school in Gloucester County, Virginia, U.S. is seen in an undated photo. Crystal Cooper/ACLU of Virgina/Handout via REUTERS

In canceling planned arguments in a bathroom access lawsuit brought by a Virginia transgender high school student, the justices declined to resolve whether transgender students are protected by a law, Title IX of the Education Amendments of 1972, that bars discrimination on the basis of sex in education.

Bathroom access has become a key issue in the intensifying battle over transgender rights. North Carolina last year became the first state to require people to use bathrooms matching their gender at birth in public schools and government buildings. About a dozen other states are considering similar measures.

President Donald Trump’s administration last month rescinded guidance given to public schools last year by former President Barack Obama’s administration to permit transgender students to use bathrooms that correspond to their gender identity.

“We had emphasized this is an urgent situation for transgender students,” said Joshua Block, a lawyer with the American Civil Liberties Union who represents Gavin Grimm, the student who brought the case that the Supreme Court dodged.

Block said the justices’ action, which threw out a lower court ruling favoring Grimm and instructed that court to reconsider the matter in light of the Trump administration’s stance, was “justice delayed not justice denied.”

In the meantime, the question of whether Title IX protects transgender students will continue to be litigated in lower courts and mostly likely will be decided by the Supreme Court in the coming years, perhaps as early as 2018.

A handful of cases are pending in federal courts, including Grimm’s, all of which could reach the Supreme Court. Courts are also set to decide the related legal question of whether school policies that limit access to bathrooms violate the U.S. Constitution’s equal protection guarantee.

In Grimm’s case, the Richmond-based 4th U.S. Circuit Court of Appeals will now take a second shot. Its earlier ruling had been based on the Obama administration’s interpretation, now reversed by Trump, that Title IX protects transgender students.

The 4th Circuit separately is due to hear arguments in May in a challenge brought to the North Carolina law, which still may be repealed following a public outcry against it.

In the most recent ruling, a federal district judge in Pennsylvania on Feb. 27 decided in favor of three transgender students who attend Pine-Richland High School in the Pittsburgh suburbs. The court ruled that the school’s refusal to allow the students to use the bathroom that corresponds with their gender identity violated their constitutional rights.

Other cases are pending in Illinois, Ohio and Wisconsin.

“We expect and urge all schools to meet their moral and legal responsibility to fully respect and include their transgender students, as thousands of schools around the country have already been doing for years,” Mara Keisling, executive director of the National Center for Transgender Equality advocacy group, said after the high court’s action.

Tony Perkins, president of the Family Research Council Christian conservative advocacy group, said the Supreme Court’s action “provided good news to parents and students concerned about privacy and safety in school showers, locker rooms and bathrooms.”

“State and local officials working together with parents are best equipped to design policies that respect the dignity, privacy, and safety concerns of all students,” Perkins said.

By the time the transgender bathroom issue returns, the Supreme Court, which has been down one justice for nearly 13 months, likely will have its full complement of nine justices. If Trump’s high court nominee, conservative appellate judge Neil Gorsuch, is confirmed by the U.S. Senate, the court would once again have a conservative majority. Gorsuch’s confirmation hearing is due to start on March 20.

Transgender rights advocates remain hopeful that conservative Justice Anthony Kennedy, the court’s regular swing vote who ruled in favor of gay marriage in 2015, will side with the court’s liberals on upholding transgender rights.