President Donald Trump moved to end a decades-old immigration policy known as birthright citizenship when he ordered the cancellation of the constitutional guarantee that U.S.-born children are citizens regardless of their parents’ status.

Eighteen states have sued the federal government over the executive order, showing the legal challenges the president will face.

Two dozen Democratic-led states and cities are challenging President Donald Trump’s bid to end birthright citizenship in court, a major constitutional challenge to one of the White House’s signature policies.