Again - stop them from entering how?  With bullets?  Into the bodies of men, women and children?  Refugee policy does apply if they are at risk of being deported to an unsafe country as the Trump admin is doing.

We can invoke notwithstanding and stand at the border waving it at everyone but it has no impact whatsoever. 

I don't think the hysterics of "invasion" are helpful either.  We don't know these peoples' situations.  
We are taking them in, assessing matters and then will decide.  
In a civilized manner. 
As we have always done.

There are more than we're used to, the USA is more volatile than usual and we have our own hatemongers stirring fear of invasion.  Let's calm down and deal with the problem without the hysteria.