How can DC mayor call in troops from other states legally, would it not require the president?
You are still thinking laws apply.
Plus the DC mayor has no authority.
“Under federal law the Mayor of the District of Columbia does not have authority over the Guard, and we must receive approval from the Secretary of Defense before we’re able to send the Maryland National Guard across the border into the federal city into the District of Columbia.”
“For state missions, the governor, through the state Adjutant General, commands Guard forces,” they write online. “The governor can call the National Guard into action during local or statewide emergencies, such as storms, fires, earthquakes or civil disturbances. In addition, the President of the United States can activate the National Guard for participation in federal missions.”