Ms. Brighton, who estimated her annual income (after her business failed) was under $10,000, did not realize that the RRSP withdrawal she made in 2011 "would affect her GIS entitlement." Because of it, her income exceeded the "threshold for payment of GIS benefits, which was $16,512 for the 2012-2013 benefit payment period." (Paras. 9 and 16).
It seems a harsh result and a trap into which you can fall if you try to keep yourself afloat by drawing on RSP savings.
See Brighton v. Canada (Human Resources ans Skills Developement), (2013 TCC Paris)