At stake is whether a president can impose tariffs without limits.
During Wednesday morning's Supreme Court arguments, several justices, including two of the more conservative members of the court appeared skeptical of the president's tariff authority.
President Donald Trump has said without the ability to issue tariffs, the country won't survive.
The owners of hand2mind are among the businesses that sued.
"There are hundreds and thousands of businesses in the U.S. that are impacted by this policy. They're impacted either because they they're manufacturing it, they have to pay tariffs or they're impacted because they have to buy things. So, people who are out there shopping for Christmas presents right now, maybe noticing that prices are a little higher or inventories a little short," said Elana Ruffman, vice president of marketing and product development for hand2mind. "The core issue at stake in this case is separation of powers. So who has the right to taxation? Is it Congress or is it the president?"
They said, the heart of this case is about taxation without representation.
Learning Resources, another Vernon Hills business, is also involved.
The Supreme Court's decision could cost Americans thousands or trigger tens of billions in refunds.
Justices heard hours-long arguments Wednesday.
The White House is leaning on a 1970 emergency law, the International Economic Emergency Powers Act, or IEEPA, to allow the president to impose tariffs on dozens of countries.
"President Trump has negotiated agreements worth trillions of dollars with major trading partners on minding those agreements he has warns would expose us to ruthless trade retaliation by far more aggressive countries," U.S. Solicitor General D. John Sauer said.
"I just don't understand this argument; it's a Congressional power, not a presidential power to tax. And you want to say tariffs are not taxes, but that's exactly what they are," Justice Sonia Sotomayor said.
Trump is the first president to try use the IEEPA to set tariffs without Congress.
"We have 500 employees who work for us. We're a mission-driven family business, and it's really important for us to be able to maintain those jobs," Ruffman said. "This dramatic tax increase really affects our ability to provide stable jobs."
This is also the first time the high court has had to examine IEEPA's meaning.
Experts say the ruling could come down to a war over words.
"Tariffs were never mentioned in the (International Economic) Emergency Powers act; so it's questionable that they should use those arguments in the first place," said Phillip Braun, a clinical finance professor with Northwestern University Kellogg School of Management.
If the Supreme Court sides with the president on tariffs, it would mark a major expansion of presidential power.
A ruling is expected before next summer.