I saw this in a playoff game this weekend. A receiver catches a deep pass and heads to the end zone. As he crosses the goal line, the DB "slide tackles" (yes, the soccer tackle) him from behind. The official on the play throws a flag and signaled for the kid to leave the field. In the stands we assumed he had been ejected. Then the Referee waves the flag off and the kid comes back on the for the try.
I know tripping is legal under federation rules, but does that include a slide tackle? As I type this, it sounds okay, but it sure looked like something that should not have been allowed.