PPACA's 5 biggest moments

Photo: Health and Human Services Secretary Kathleen Sebelius listens as she testifies on Capitol Hill in Washington, Thursday, April 10, 2014, before the Senate Finance Committee hearing on the HHS Department's fiscal Year 2015 budget. (AP Photo/Susan Walsh)

The employer mandate delays

Though a number of the law's components have been delayed over the years, the one with the most backlash was PPACA's employer mandate — which became a lightning rod for criticism of the law.

The provision — once thought of as a key, if not essential, part of PPACA — since its inception has been vehemently attacked by employer groups and business owners. Originally scheduled to go into effect in 2014, the mandate was twice delayed by the administration, which said it needed more time to implement the provision. Those delays called into question whether the provision would ever be implemented, and whether the provision was even needed in the law.

Attention to the mandate hit a new high at the Benefits Selling Expo in April 2014, when Robert Gibbs predicted during a keynote address that the employer mandate would never be put into effect.

"I don't think the employer mandate will go into effect. It's a small part of the law. I think it will be one of the first things to go," he said to a notably surprised audience.

Gibbs was proven wrong when the updated January 2015 deadline stuck for employers with more than 100 employees, who had either to offer insurance or pay a fine of $2,000 per worker. Meanwhile, employers with between 50 and 99 employees have until January 2016 to offer health insurance or pay a fine. Companies with fewer than 50 employees are exempt.

Photo: Former White House Press Secretary Robert Gibbs. (AP Photo/Pablo Martinez Monsivais)

Subsidies challenge

In late 2014, it was announced that once again the Supreme Court would hear an important PPACA case, this one on the federal subsidies under the law.

The case, King v. Burwell, ultimately hinges on just four words — "established by the state" — as it calls into question the legality of federal exchanges. While PPACA challengers say that phrase limits the tax credits to the 16 states that have set up their own exchanges, the Obama administration has defended an IRS rule that interpreted the law as allowing subsidies nationwide.

Read: 5 things to know about SCOTUS subsidies case

Of course the decision has huge implications. Ruling the subsidies invalid could unravel the law, making other core provisions ineffective and potentially causing the market for individual insurance policies to collapse. And, invalidating the subsidies could boot nearly 10 million from health coverage and cause crushing premium increases for millions more.

The Supreme Court heard oral arguments on the case March 4. It is expected to make a decision by June.