The U.S. Supreme Court on the 20th ruled that the Donald Trump administration's country-by-country reciprocal tariff was unlawful, but projections say the trade environment with the U.S. will not change significantly.

President Lee Jae-myung shakes hands with U.S. President Donald Trump as he arrives at Gyeongju National Museum during last year's APEC summit in Gyeongju, North Gyeongsang Province. /Courtesy of the Presidential Office

The reciprocal tariff has been nullified, but the U.S. could pull out a "substitute tariff" card and impose high, item-specific tariffs on core industries such as automobiles.

With the Trump administration holding many trade tools it can deploy, the prevailing view is that it will be realistically difficult to overturn the Korea government's pledged $350 billion (about 505 trillion won) in U.S.-bound investment.

Korea, after pledging large-scale investment in July last year, led an agreement to lower the reciprocal tariff and the automobile tariff to 15%, but this ruling does not limit the authority to impose item-specific tariffs on products such as automobiles.

The Trump administration has already emphasized policy continuity through "Plan B." Experts projected that a stronger substitute tariff could be introduced in place of the reciprocal tariff.

Jamieson Greer of the Office of the United States Trade Representative (USTR) said in a recent Fox News interview, "We will find a way and use other tools," signaling an intent to maintain the tariff regime by using Section 232 of the Trade Expansion Act or Section 301 of the Trade Act.

The ruling opened a path for domestic export corporations to be refunded the tariffs they have paid, but actual refunds are expected to be difficult. With more than 1,000 corporations worldwide filing suit, the procedure is complicated because, depending on the transaction structure, they must prove who actually bore the tariff.

Meanwhile, the Korea government is said to be preparing response plans by scenario while watching for the Trump administration's corresponding measures following the Supreme Court ruling.

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