Chicago Mayor Rahm Emanuel [official website] delivered a letter [PDF] to US President-elect Donald Trump Wednesday signed by many US mayors warning of the potential economic losses Trump could cause if he repeals Deferred Action for Childhood Arrivals (DACA) [official website]. DACA allows undocumented young immigrants to remain in the US if they arrived before they turned 16 and are currently working, pursuing higher education or serving in the military. The letter, which was signed by the Mayors of New York City, Los Angeles and San Francisco among others, warned [press release] that repealing DACA could result in a loss of $9.9 billion in tax revenue over four years and $433.4 billion in US gross domestic product over 10 years. Emanuel wrote:

Ensuring DREAMers can continue to live and work in their communities without fear of deportation is the foundation of sound, responsible immigration policy. Ending DACA would disrupt the lives of close to one million young people, and it would disrupt the sectors of the American economy, as well as our national security and public safety, to which they contribute. We encourage your Administration to demonstrate your commitment to the American economy and our security by continuing DACA until Congress modernizes our immigration system and provides a more permanent form of relief for these individuals.

US Immigration law [JURIST backgrounder] and immigrants’ rights has been hotly contested in the aftermath of DACA and Obama’s 2014 executive action [JURIST report] on immigration reform. In early December 2014 17 states filed suit [JURIST report] against the president for his executive action, asserting that the order was an attempt to re-write law, a power designated solely for Congress. Later the same month a district court found parts of the same executive order unconstitutional [JURIST report] based on a finding of a violation of separation of powers and the Take Care Clause of the constitution. Last week the US House of Representatives passed [JURSIT report] a funding bill that contained amendments that would block the executive order, and remove funding from the president’s DACA program.