You'll have to give us a clue on what grounds. It's not the much abused interstate commerce clause.
Personally, I don't think the fence will be completely effective. Maybe 75%, but Americans would take that for starters.
So we have common ground. I believe that a fence will cause problems with legitimate business, as well as proving a teency weency inconvenience for the worthless coyotes and smugglers. For starters, I would LOVE an exclusionary zone for South American and Mexican criminals. Yet I am called an extremist for demanding that Mexico enforce this, upon pain of military action. Others say let us quietly build a wall, and elect more people to pick our pockets. This is a schizophrenic approach, IMHO.