Wouldn't it be nice?  President Trump is absolutely correct.  We need to send them back immediately and not EVER let them into our country.  The problem with that scenario is that these immigrants cannot set even ONE TOE onto U.S. soil or we can legally do nothing to keep them out (according to what I heard this morning from Judge Napolitano).  Now what kind of a stupid law is that?  Well, nevermind, it is the law.  Sooooooo, we need to catch these people before they get across onto the U.S. side of the fence.

https://www.lewrockwell.com/2018/06/no_author/trump-demands-immediate-deportation/

If we (the USA) would adopt a policy sorta like what Hungary has, that would be a lot easier to accomplish.  They have it set up where there is a stretch of land just outside their border fences encompassing about a 1 mile wide piece of ground and that ground is considered "neutral land".  We need to keep ALL of the trespassers in that area until they are vetted for "merit based entry".   THAT is where the Border Patrol would play a VERY useful role in helping both sides.

That is the most sensible option I can come up with, anyway.