After Boston suspects ID 'd , politicians start blaming immigration system . Alden : Perfect screening is impossible and would n't have prevented the bombings . Comment: We need immigration reform , but must be realistic about what it can and ca n't do .
After Boston suspects ID 'd , politicians start blaming immigration system . Alden : Perfect screening is impossible and would n't have prevented the bombings . The U.S. ca n't shield itself with better screening or by keeping immigrants out . We need immigration reform , but must be realistic about what it can and ca n't do .