The protection of a sovereign state's border is the States responsibility, first. It is to be done by the Organized County Militias, (see the 2nd Amendment in The Constitution for the United State of America) that is men between 18 and 45 years old. Since we have a National Guard (which is not Constitutional) it may also be utilized. The Federal Government is to be allowed only if asked by the State Governor.
The Organized Militia which is clearly stated in the 2nd Amendment of The Constitution for The United States, must be reestablished immediately. It has been suppressed for decades by the FBI/CIA Cabal and that must be stopped immediately! The County Sheriff is in charge of the Militia and the people have authority over the Sheriff.
See Brent Winter's website www.CommonLawyer.com to learn about the Militia which is the heart of the 2nd Amendment. The 2nd Amendment is about the Militia, not guns.
Martial Law is way out of line for this matter but, the president could declare these events "an invasion' and put armed military on the border. Currently we have unarmed military on the border.
President Trump has the authority, under an Executive Order of March 1, 2017, to use Martial Law at any time and we have technically been operating under Martial Law since Abraham Lincoln and the Ciil War.