The Immigration and Naturalization Service reassigned four midlevel employees today in the wake of the agency issuing visa approval notices for two Sept. 11 hijackers six months after they flew airliners into the World Trade Center. The immigration commissioner, James Ziglar, said the breakdown that led to the notices being issued ``is unacceptable and will not be allowed.’’ No one was fired. Attorney General John D. Ashcroft also asked Congress today to give him back authority to fire INS employees for violating Justice Department rules. That power was not included in the current budget proposal. ``It is essential that I...