WASHINGTON (Yonhap) ― A new law went into effect in the U.S. state of Virginia Tuesday, requiring local school textbooks to use the South Korean name “East Sea” alongside the more commonly used Japanese name “Sea of Japan” for the body of water between the two countries.

The landmark legislation passed through the Virginia House of Delegates in February, despite strenuous Japanese government lobbying against it, and Gov. Terry McAuliffe signed it into law in April. Virginia is the first U.S. state to take such action on the issue.

Though the law took effect Tuesday, new school textbooks bearing both names of the sea will likely be used beginning in 2017 because Virginia’s government reviews new school texts every seven years. The next review is set for 2016 for texts to be used from the following year.

But Korean-American activists campaigning for the East Sea name say that dual-name textbooks can be used broadly in the U.S.

earlier than expected because many publishing firms have already started adding the Korea-favored name to their texts.

“There won’t be any tremendous change overnight just because the law took effect today, but I believe it will ultimately bring about much bigger and broader changes than expected,” said Peter Y.

Kim, head of the Voice of Korean Americans, an organization that has campaigned for the measure.

Koreans argue it’s important to teach the historic background on why the water is more widely known as the Sea of Japan than its original name, the East Sea. They say it’s just a relic of Japan’s imperialistic past, including the 1910-45 colonization of Korea.