Since most of the lands west of the Mississippi were Spanish or Mexican land at the formation of the US, those 'illegals' are actually returning to the land we stole from them fair and square.  Texan war of independence so they could have slavery which was banned by those heathen mexicans.  Or The Mexican war and other threats whereby we got AZ, Cal. Ore. N.Mex. Colorado, etc.  But we did it legally by killing the opposition.