The Nuclear Regulatory Commission denied a petition (local pdf) from the Natural Resources Defense Council (NRDC) that requested NRC

to amend the regulations that govern domestic licensing of production and utilization facilities, and special nuclear material to establish a date when the NRC will no longer license the use or export of highly enriched uranium (HEU) except for restricted use by a few specialized facilities.

In particular, NRDC cited exports of HEU to Canada as a practice to be discontinued. NRC declined the request, arguing in its response (local pdf) that the current NRC regulations are adequate.