Is liquid measured by liter or weight?

Dear Editor,

I called Consumers Affair to find out if liquid should be measured by liter or weight? A staff told me that he had to find out and call me back but he thought liquid should be by liter. Got a call saying that he was advised it was OK to measure liquid by weight. This took me by surprise. There’s a detergent store that sells liquid detergent by weight and not by liter. I need an advice to know if there’s a change that I don’t know of; is liquid be measured by weight now?

Sincerely,

L. Hicks