The U.S. Department of Homeland Security has been unable to meet the requirements of a law passed by Congress after 9/11 that states non-U.S. citizens must go through a biometric collection process both upon entry and leaving the country.

This law was enacted to track visitors’ actual length of stays against what they were permitted to do and sanction those who overstayed their visa.

As David Heyman, assistant secretary for policy at the DHS, writes in USA Today, the country’s infrastructure doesn’t support biometric exit processing. The DHS’ pilot programs in 15 airports showed limits in existing technology and lack of infrastructure at airports and border checkpoints. Creating a program to comply with the law could cost $3 billion or more, the department claims.

Heyman notes that the DHS has instead worked on enhancing its existing system to match passport information at arrival and departure. This now gives the department the ability to know who has overstayed a visa and can action against those people.

Read more here.