The relevant rule seems to be:
3.7.5. wrote:Gripping the striking surface of an opponents Weapon results in the disabling of that limb.
Note that 3.7.5 mentions "striking surface" which I would interpret as being the edges of the sword, not the flats.
However, this action could theoretically be interpreted as being illegal due to this rule:
1.4 wrote:Creative interpretation of the rules to gain any advantage is discouraged. These rules are intentionally sparse to allow for ease of use. The Marshal, according to these rules, and medieval foam combat precedent, settles all disputes.
If you were a marshal and witnessed this, would you call anything on the person who pinned his opponent's weapon?
Assuming you don't see a problem with the above action, how would you interpret that if the blade were to suddenly twist, such as if the person is attempting to pull the weapon out of the pin, causing the striking surface(s) to come in contact with the body and arm?