If what dirtboy said is true, then they don't have a right to protect themselves or their property; they only have a right to call 9-1-1 and then maybe some LEO will do something about it, in his abundance of discretion, after some suitable period of time passes during which your family become corpses.
You have the right to remonstrate in strong language, and to urge the felons on your property, in your best imitation of Judith Martin starchiness, to leave your property posthaste!. Then, after they stop laughing, you are in God's hands -- and theirs.
From what I understand, most LEO are instructed to not get involved in illegal border crossers. In some area's they cannot apprehend illegals on the basis that LEO's suspect they are border-busters...they can however stop the illegals for some other crime-related reason and take it from there. What typically happens is LE is told to let them go. It varies from area to area...I know in my part of the state, illegals cannot be detained by the law unless they commit another crime. States and counties are not financially equipped to deport. Thats the job of the INS. INS tells the LE to take names and let them go and the illegals vanish into the American urban-scape. Our entire system is exploited and taken advantage of, while US, the law abiding tax payers get stuck footing the bill for squatters. I think some duties of the INS should be disolved and the funding go to the individual states so that state and local LE agencies have the means to track, enforce and deport illegal aliens.