"Do you think that an illegal crossing of the border is still legal for some but not for others?"  Good grief.  I certainly didn't mean to say THAT.  If it sounded like it, shame on me.  An illegal crossing is an illegal crossing.  

As for your question, "Which part of the US Constitution or immigration law provides more right for a Mexican to cross the border illegally for a Mexican than for a French national?"  See my above response.