Ok so i've read the description about shackles only being acceptable to use when someone accepts to be shackled or subdued.

However I wondering if it was also acceptable to shackle someone if they were knocked down. Stunned, or any other effect that causes the character to become immobile. Any thoughts on this?

Subdualed or held would be prefered, as these other methods are a much more short term form of incapacitation.