It's working already
From the looks of these posts it seems the mere mention of such policy is already keeping out many undesirables. It's amazing our these same legislators supported eavesdropping electronically on Gen. Flynn. The United States police already have the authority to impound cell phones in the event of an accident or crime. DHS probably can attain the info over megadata programs once visas are obtained by cross referencing so it seems like a waste of resources to obtain it individually. But if terrorists were committing terrorist attacks there would be no need for any of these policies. Too bad our traitorous legislators don't know who the enemy is.