"No one is above the law - not even the President," Ferguson said in a statement. "And in the courtroom, it is not the loudest voice that prevails. It's the Constitution."
Other Washington-based tech companies that expressed support for the lawsuit include Microsoft, which pledged to testify and provide supporting evidence for the case, and Expedia, an online travel-booking firm.
Since Trump's executive order was unveiled on Friday, major tech companies including Google, Apple and Facebook have sharply and publicly criticized the Trump administration. Some companies have recalled employees based in the seven countries -- Iran, Iraq, Libya, Somalia, Sudan, Syria, and Yemen. Others, such as Microsoft, said they are offering special legal assistance to help their workers travel to the United States. On Monday, scores of Google employees and Sergey Brin, one of the company's founders whose family fled as refugees from the Soviet Union, took to the streets to protest Trump's immigration ban.
Based in Seattle, Amazon did not answer questions on how many of its employees may be affected by the order or what Bezos meant when he wrote the retailing giant was exploring "other legal options." Bezos's letter said the company had spoken to lawmakers and "senior administration officials" to express its opposition to the policy.
Ferguson's lawsuit is the first by a state to challenge the executive order. But other attorneys general are also mulling legal action, including Eric Schneiderman, the attorney general of New York, according to his spokeswoman Amy Spitalnick.
