According to what I've read, in the US, the enforcement is weak. (from Forbes)
If anyone gets arrested, it is because of the fraud committed that led to the short selling e.g.: inside info, fake PR's and the 911 terrorists etc,........not the actual short selling.
Other countries are more strict: Australia and Malaysia have been known to arrest people just on short selling.
If anyone got arrested, it was based on fraud and not short selling.