According to the MODS tag library, accesscondition is for "information about restrictions imposed on access to a resource." An explicit statement that there *are* no restrictions is definitely information about restrictions, so I'd say that this is exactly the right place for it :)
From: Metadata Object Description Schema List <[log in to unmask]> On Behalf Of Vicky Phillips
Sent: Friday, May 10, 2019 11:07 AM
To: [log in to unmask]
Subject: Re: [MODS] Oral history collection metadata
> I should say that there are not any records that say “Subject did NOT consent”.
> Therefore this metadata does not fit under Access Conditions, I think, since if we
> have the resource it means that subject has consented. These text statements
> merely serve as proof to the user.