As far as we know, they're not officially banned, but neither wants the scrutiny that would come from showing up at a gathering of tens of thousands of players who blame them for money lost at Full Tilt Poker. Both are being held responsible by the poker world for Tilt's inability to refund deposits when the site was shut down by the DoJ on "Black Friday" in 2011. Money that was supposed to be held separately for repayment was allegedly used for other purposes, including disbursements to Ferguson, Lederer, and other principals. To avoid the certain consternation and scrutiny they'd face, neither has appeared at the WSOP, nor any poker-related function of any kind, since Full Tilt went down.
As for the WSOP's stance on the matter, we've never seen an official rebuking of Ferguson or Lederer; however, there's one big tell that conveys their position: Chris Ferguson's picture is not among the photos of past WSOP champions on the walls of the Amazon Pavilion. Of the past 43 champions, all appear in order (based on the year they won), except for three.
Ferguson won the Main Event in 2000, so his picture should hang between 1999 winner Noel Furlong and 2001 winner Carlos Mortensen, but Mortensen follows Furlong with Ferguson nowhere to be found.
The second exception is associated with Russ Hamilton, who won in 1994. Similar to Ferguson and Lederer, Hamilton has served a self-imposed exclusion from the WSOP to avoid public ridicule over his part in the Ultimate Bet hole-card scandal. Russ' picture is still up; however, there's a curtain over it so only his name and the year are visible.
The third is 1985 winner Bill Smith, whose picture is also not displayed. One of Anthony Curtis' favorite WSOP stories is about Smith's final table. Billy was a wild man and an inveterate drinker while he played, but not on that final table, where he'd gone most of the way drinking only water. Finally, he couldn't stand it anymore and ordered a Budweiser. When the cocktail waitress delivered the Bud, the packed house at Binion's Horseshoe erupted in laughter and applause. Smith went on to dominate and win the bracelet. No one we talked to knows for sure why the late Bill Smith's picture is missing and we were given several possible reasons when we tried to find out. One was that they couldn't find a photo where he wasn't drinking and smoking, but the prevailing belief is that Smith's family wanted to be paid for the photo's use and the WSOP declined. We don't have complete verification, but the story rang true with a few veterans that we ran it by.