The IRB have issued new Regulations for Subsititutes and Uncontested Scrums
THE 'MAN OFF' RULE

The RFU have issued a new Regulation - which supersedes that printed in the 2009 -2010 Handbook - for Front row Replacements and Uncontested Scrums.
This is a long document (see below) - which includes the 'Man Off' rule.

This is designed to remove any advantage that a Team may wish to gain by going to Uncontested scrums.
New regulation 3.4 (c)
"If on any occasion where uncontested scrums are ordered by the Referee as a result of there being no suitably trained and experienced front row replacement for any reason (which includes injury, temporary blood injury, temporary exclusion (i.e. following a yellow card) or permanent exclusion (i.e. following a sending off)), the team concerned shall not be entitled to replace the player whose departure caused the uncontested scrums. On return to the field of play of the front row player who has been temporarily excluded or injured the Match shall continue with contested scrums."   

The regulation is 6 pages long and includes details of Replacements permitted at all levels. 
Clubs are recommended to download the new Regulations and replace the version in the 2009-2010 Handbook.

To view the content of the RFU Regulations please visit  www.rfu.com/regulations
or open the pdf below