As soon as she heard the US Supreme Court had struck down President Donald Trump's authority to impose sweeping global tariffs, Jenelle Peterson's mind raced to the possibilities for her toy business.

She might import more toys to the US and invest in designing new ones - things she had put on hold as Trump's levies on China, where her Canadian firm Wild Life Outdoor Adventures makes its products, took a 25% bite out of her profits last year.

Still, uncertainty about refunds and other tariff authorities that the Trump administration might leverage is keeping her on edge.

"I have a bit of reservation in too much celebration," she said. "But for us, every percentage point matters."

Many business owners greeted the Supreme Court's ruling with cautious optimism.