I am assuming you are importing a flat file into SQL Server via SSIS. If so, the limitations I know of are only based on the amount of memory you have available to SSIS and in the database. If you max file size is 10 GB, you won't be able to put more than 10 GB into the file.
If the file being loaded into memory is 10 GB and SSIS only has 5 GB to work with, I think it will page to disk or possibly fail (offhand, I do not remember the behavior, but I think it pages to disk which will be incredibly slow).
If you are meaning something else by "importing into SQL" than through SSIS, could you elaborate?