The abortion link
The Hahn family, owners of Conestoga, and the Green family, owners of Hobby Lobby, said some of the mandated contraception prevent human embryos from being implanted in a woman's womb, which the plaintiffs equate with abortion.
That includes Plan B contraception, which some have called the "morning after" pill, and intrauterine devices or IUDs used by an estimated 2 million American women.
A key issue for the bench has been be interpreting a 1993 federal law requiring the government to seek the "least burdensome" and narrowly tailored means for any law that interferes with religious convictions.
Chief Justice John Roberts could be the "swing" vote as he was two years ago when siding with the court's more liberal members to allow the law's "individual mandate" to go into effect.
That provision requires most Americans to get health insurance or pay a financial penalty. It is seen as the key funding mechanism to ensure near-universal health coverage.
Searching for compromise?
But how will the divided court rule this time?
Unanimous opinions in recent days on separate issues involving presidential recess appointments, cellphone searches by police, and abortion clinic protests suggest Roberts may be on a private campaign to push his colleagues to rule narrowly to reach consensus.
Such an approach usually involves both left- and right-leaning justices reluctantly giving a little.
"At oral argument it seemed likely a majority of the justices were looking for a compromise," said Goldstein, "in which the closely held for-profit businesses wouldn't themselves have to pay for contraception care, but the employees would get it, maybe through the exchanges, maybe financed by the federal government."
Compromise may be nice, but as other contentious cases earlier this term demonstrated, it is not always easy to achieve.
Separate decisions this spring involving political campaign donations and voter-approved affirmative action limits produced especially sharp 5-4 divisions.
Under the Affordable Care Act, financial penalties of up to $100 per day, per employee can be levied on firms that refuse to provide comprehensive health coverage. Hobby Lobby, which has about 13,000 workers, estimates the penalty could cost it $475 million a year.
The church-state issue now in the spotlight involves rules negotiated between the Obama administration and various outside groups. Under the changes, churches and houses of worship are completely exempt from the contraception mandate.
Other nonprofit, religiously affiliated groups, such as church-run hospitals, parochial schools and charities must either offer coverage or have a third-party insurer provide separate benefits without the employer's direct involvement. Lawsuits in those cases are pending in several federal appeals courts.
Monday's decision could signal how the court will approach other lawsuits against the health care law.
"We're now getting the second generation of challenges to the Affordable Care Act -- about the actual adoption of the statute, and its core provisions," said Goldstein. "We're probably going to see cases over the next five to ten years, as more and more details about the law get put into effect."