[zaptheimpaler]

This is the crucial point:

> The proposal circulated in the form of an internal memo in the Department of Homeland Security (DHS), which oversees citizenship and immigration, intends to end the provision of granting extensions to H-1B visa holders whose applications for permanent residency (Green Card) had been accepted.

It has always been at discretion of USCIS, who usually follow internal policy - in practice it is like a law, but more flexible and easier to change for lawmakers. Until now the policy has generally been to allow visa extension indefinitely while waiting for a green card, and this memo may end that.