Can a label only refer to input elements?

Question

W3Schools have this to say about labels:

The tag defines a label for an input element. _{[Emphasis mine]<}

Answer 1

According to the W3C it applies to Form Controls, and Form Controls are defined as:

• Buttons
• Checkboxes
• Radio buttons
• Menus
• Text input
• File select
• Hidden controls
• Object tags

So FireFox is technically right, although I'd hardly consider it to be "breaking" if a browser didn't restrict it to those elements.