Maryland joined 17 states, Washington, D.C., and San Francisco to sue President Trump on Tuesday over what they called his “flagrantly unlawful attempt” to end birthright citizenship through one of the flurry of executive orders he signed after taking office.

Maryland joined more than a dozen other states on Tuesday in challenging President Donald Trump’s executive order to end the birthright citizenship the U.S. extends to all people born in the country regardless of their parents’ legal status.

A day after President Donald Trump signed a slew of immigration-related orders, multiple states had sued to stop his plan to end birthright citizenship, and experts were scrutinizing the implications of sweeping directives to bar asylum and more.