Democratic attorneys general from 18 states have already organized and filed a federal lawsuit against President Donald Trump’s executive order to eradicate birthright citizenship for the children of illegal immigrants and temporary visitors to the country.

The lawsuit was filed in Massachusetts on Tuesday, just hours after Trump took executive action late Monday evening to bar the children born to illegal immigrants in the United States from automatically becoming U.S. citizens. Only U.S. citizens and permanent residents may automatically assume U.S. citizenship for children, Trump maintained.