Washington State Attorney General Bob Ferguson plans to depose Trump administration officials to determine "what truly motivated" the president to issue his travel ban if his case against the executive order makes it to trial.

Ferguson, a Democrat, made headlines earlier this month when a federal judge in Seattle issued a restraining order against President Trump's travel ban, effectively blocking the administration from implementing the executive order.

The state attorney general said Sunday on ABC's "This Week" that emails or other correspondence between Trump administration officials could reveal a coordinated effort to impose an unconstitutional ban on Muslims seeking to enter the United States.

Ferguson said he will use "every tool" he can to make such discussions public.