Is it too late to register to vote in Ohio by now?
If it is, you can just check the registration of the volunteers.
And even if it's not too late to register to vote, I would think that the date of registration is available and the RNC can beware of those who recently registered Republicans.
If the infiltrators take on identities of real people, they can be prosecuted for identity theft.
Voter registration deadlines here in Ohio have passed.