Chess Competition rules Touch and move law
There are a few famous cases where players appeared to break this rule without being punished. The most famous example was by the then World Champion Garry Kasparov against Judit Polgar in a top-class tournament. Seeing that 37.Bb7-c6 would be bad for Black, Mr. Kasparov instead put the knight on f8. However, the way Miss Polgar saw it, Mr. Kasparov's hand 'did' leave the piece on c5. Accounts diverge from there.