Back in 2007, the Raiders were popped for violating rules during the offseason OTAs. These sessions are non-contact and generally more laid back than training camp. There are also some restrictions on how long the players can be on the field each day and even at the facility.
Three years passed before there was another team penalized for violating the rules during OTAs. There were four teams busted this year and two today.
The penalty is usually a loss of a few days of OTAs (teams are allowed 14 total).
The way the process works, from what I can gather, is that a player would have to report the violations to the NFLPA and they would then file a complaint with the league.
The Chiefs probably had to be a little careful because they are the only team in the NFL with two players on the NFLPA executive committee -- Brian Waters and Mike Vrabel.
So if you're hearing all this news about teams violating the rules at OTAs, you can be confident that the Chiefs were not one of those teams.