Unzip Etiquette

I was surprised today to notice a man unzipping his fly as he walked into the public restroom. He didn’t wait till he was at the urinal.  He did it as he entered. I wondered if Emily Post has a rule about that.
 

I was surprised today to notice a man unzipping his fly as he walked into the public restroom. He didn’t wait till he was at the urinal.  He did it as he entered.

I wondered if Emily Post has a rule about that.