Incomplete or Illegal Participation?

[insatty]

I have looked at the authorities noted in the replies. But those don't appear to definitively answer the question whether A89 made a legal catch when he alights from OB, possesses the ball, and arguably comes down in bounds. I was able to sell my ruling because A89's first-touching foot was right at the sideline. Had A89 had both feet in bounds when he made the catch, then its illegal participation without question. But do I have a catch? If so, then I booted the call.