President Donald Trump is vowing to take his tariff case to the Supreme Court after a federal appeals court ruled his sweeping scheme was illegal — but according to New York-based attorney John Polonis, the president shouldn't bank on the 6-3 Republican judicial body to give their stamp of approval, either.

Polonis laid out why he believes the justices are likely to uphold the appeals court's ruling in a lengthy post to Threads on Monday.

The appeals court, Polonis explained, had solid reasoning when it decided 7-4 that Trump cannot use the International Emergency Economic Powers Act, or IEEPA, to set new tariffs on whatever goods he wants.

"The appellate court held that the Constitution vests 'The core Congressional power to impose taxes such as tariffs ... exclusively in the legislative branch.' This is what I have argued from the start and why I've never understood Trump's strategy," wrote Polonis. "Notably, the IEEPA is an emergency law that was designed to impose economic sanctions in response to threats against the U.S.As the court noted — it makes no mention of tariffs. There's no indication Congress intended to transfer any of its tariff power to the executive."

A section of the act mentions "regulation" and "importation" — but, said Polonis, "the court said that the phrase where they appear 'to include imposing these tariffs is ‘a wafer-thin reed on which to rest such sweeping power.' And no other President has attempted such a power grab."

Trump has also claimed he has the authority as a matter of national security — but the court didn't see this as a national security matter, Polonis continued, instead being an issue of the power of the purse, which is strictly a power given to Congress.

"The Supreme Court has an important job now. What are the limits on executive power? Is one man above the Constitution? Can Congress abdicate its responsibilities because it's in bed with the President?" Polonis concluded. "It will be very hard for them to overcome the constitutional arguments at the appellate level unless they're willing to further reveal the extent of they're willing to go to protect this President."