I don't know about open borders, but I understand the Johnson's stance on illegal immigration is to cut off the magnets.
You might want to review his web site on this issue.
https://www.johnsonweld.com/immigrationHaving served as Governor of a border state, Gary Johnson understands immigration. He understands that a robust flow of labor, regulated not by politics, but by the marketplace, is essential.
He understands that a bigger fence will only produce taller ladders and deeper tunnels, and that the flow of illegal immigrants across the border is not a consequence of too little security, but rather a legal immigration system that simply doesn’t work. Militarizing the border, bigger fences, and other punitive measures espoused by too many politicians are all simplistic “solutions” to a problem caused by artificial quotas, bureaucratic incompetence and the shameful failure of Congress to actually put in place an immigration system that matches reality.
Governor Johnson has long advocated a simplified and secure system of work visas by which willing workers and willing employers can meet in a robust labor marketplace efficiently and economically. Aspiring immigrants would undergo a background check, pay taxes and provide proof of employment.
Making it simpler and efficient to enter the U.S. legally will provide the greatest security possible, allowing law enforcement to focus its time and resources on the criminals and bad actors who are, in reality, a relatively small portion of those who are today entering the country illegally.