We need federal law to prevent cities and states harboring illegals.
They already are. No one enforces the laws.
At this point the feds are capable of doing only a handful of things correctly:
1) Pass spending bills that have nothing to do with improving America when there is no money.
2) Print the money to cover the excess spending.
3) Cause never-ending inflation in this country.
4) Take away rights guaranteed us by the Constitution.
5) Build a border for other countries but not ours.
6) Bring in human scum from the whole world and redistribute our personal wealth.
One can get to several thousand real quick the things the gummit does real well.