national guard troops to the u.s./mexico border. the memo says the situation has reached a point of crisis and adds the security of the united states is in perilled by a surge of illegal activity on the southern border. it is unclear when the troops might actually show up at the border. a senior administration official says details are still worked out with dhs, department of defense and border states. >> the national guard mission is unclear as well. federal law bars the military from involvement in immigration enforcement. in the past when obama and bush deployed guards to the border, they worked in training roles. for more, we turn to cnn's jeff zeleny at the white house. >> reporter: dave and rene, the department of homeland security and the president want to send troops to the u.s./mexico border. this is part of president trump's directive to increase