TexasCHLforum.com

There is no definition on what is 'small', but there was a case where someone was arrested for a 'large' canister. The Grand Jury agreed to prosecute, but didn't indict, so charges were dropped. As such, no case law really exists, but the guy was out $6200 in legal fees

http://www.wfaa.com/story/local/2014/08/30/13457508/" onclick="window.open(this.href);return false;

As for what the Wylie police were trying to say, the 'key chain' sizes are what they called 'small' and not a stand-alone canister. However, it is still all discretionary from one officer to another. I really don't think the little small pepper spray cans you get on a key chain would be an issue, but if you got an overzealous officer, they might try to make it one.