SI 2021/917. The Greenhouse Gas Emissions Trading Scheme Auctioning (Amendment) (No. 2) Regulations 2021. Comes in to force 25th August. These Regulations amend SI 2021/484 The Greenhouse Gas Emissions Trading Scheme Auctioning Regulations 2021. The main changes are in the way in which the annual volume of allowances to be auctioned in a calendar year is to be calculated, the release of unused allowances originally allocated to certain industrial sectors and the processes by which the auctions are managed.