Why some countries make the legal limit 1% THC?

Looking to the countries wich are legalizating weed, they are usually making a difference between psicoactive/non psicoactive in 1%THC

As far as i know Canada, Colombia, Australia, Switzerland are doing this.

Is there any base for this 1%? or is just the first of those countries legalizing set an arbitrary limit and the others copied the legislation?

My first guess would be to distinguish/define industrial hemp and cannabis, for regulatory purposes. For example the EU draws the line between them at 0.3% I believe.