The Martha Stewart and Mark Cuban cases were more or less the same -- a non-insider investor was given information from an insider, sold their stock to avoid a loss, and were then investigated for it.

The thing is - insider trading is illegal but it's poorly defined.

Martha Stewart wasn't convicted of insider trading - she was convicted of conspiracy, obstruction of justice, and making false statements to a federal investigator.

Mark Cuban wasn't convicted of insider trading either. He wasn't convicted at all. He kept his mouth shut and the jury found him not guilty of insider trading.