The US National Archives and Records Administration (NARA) have published a proposed rule, here, that would require all users of their facilities to obtain a researcher card. At present researchers who only access microfilm resources do not need such registration.
Researchers at Library and Archives Canada, and at the Archives of Ontario, are required to have a researcher card to access all documents held. That applies to microfilm just as much as original records or those accessed through in-house computers. By contrast, in my most recent trip to the UK I found no requirement for a reader card, or even to sign in, to access substantial online, microfilm and library materials at The National Archives. A reader card is required to view original records. At the London Metropolitan Archives you are required to sign in but there is no serious identity check, even to access and handle original documents.
NARA's rationale for the enhanced requirement is to "strengthen our security to
protect buildings, people, and the records we hold" and also "help ensure more accurate counting of researchers to measure our performance in customer service delivery and to effectively allocate resources."
This change seems rather strange given another part of the proposed rule at NARA that would eliminate a three hour limit on the use of microfilm readers. The rationale is that there are no longer waits for microfilms. Apparently as the use of this equipment goes down regulation of its use needs to go up!