(Adds details and quotes on first half of oral arguments)
By Lawrence Hurley and David Ingram
WASHINGTON, March 25 (Reuters) - The U.S. Supreme Court showed no clear consensus on Tuesday about whether business owners can object on religious grounds to a provision of President Barack Obama's healthcare law requiring employers to provide health insurance that covers birth control.
During the first half of an oral argument, three justices from the court's liberal wing vigorously defended the so-called contraception mandate by firing repeated questions at the lawyer, Paul Clement, who asked the court to strike it down.
During the 90-minute argument, conservatives gave similar treatment to Solicitor General Donald Verrilli, the Obama administration lawyer defending the mandate.
The case pits religious rights against reproductive rights, with a heavy dose of politics. The challengers are arts-and-crafts retailer Hobby Lobby Stores, evangelical Christians, and a Mennonite family that owns Conestoga Wood Specialties of Pennsylvania.
Underscoring the strong feelings around the issue, hundreds of noisy demonstrators, most of them women, protested outside the courthouse in an early spring snowstorm, many under umbrellas.
Justice Elena Kagan, one of the liberals, told Clement that if the court granted the challengers an exemption from the mandate, a wide swath of other laws from Social Security to immunization health coverage would face lawsuits.
"You would see religious objectors coming out of the woodwork," Kagan said.
Justice Sonia Sotomayor, like Kagan an Obama appointee to the court, doubted whether for-profit corporations should be able to bring religious-freedom claims.
"Isn't that really the answer, that we've never before considered a for-profit corporation as exercising religion?" Sotomayor asked Clement.
Verrilli faced the opposite argument from Justice Samuel Alito, a conservative who pressed the lawyer, asking: "What is it about the for-profit corporation that is inconsistent with the free-exercise clause?" The First Amendment of the U.S. Constitution guarantees a right to freely exercise religion.
Both lawyers were repeatedly interrupted as they tried to answer the questions, rarely to the satisfaction of the justice questioning them.
The same lawyers faced off the last time the Affordable Care Act, commonly called Obamacare, was before the justices in 2012. In that case, the justices upheld by a 5-4 vote the constitutionality of the 2010 act's core feature requiring people to get health insurance.
The so-called "contraception mandate" of the healthcare law requires employers to provide in their health insurance policies preventive services for women that include access to contraception and sterilization.
A ruling is expected by the end of June. (Additional reporting by Ian Simpson; Editing by Howard Goller and Grant McCool)