Other than removing an org value from an end-user's web voucher approval group or Oracle security responsibility, there's currently no way to systematically prevent them from posting transactions to a CoA value that you've requested be disabled.
If you (or your local chart administrator) have followed all the Pre-Disable steps outlined in the Pre-Disable Checklist for Tubs found on the CSMA ABLE site prior to submitting the request to disable the value, you should not see any new transactions posting to the value during the interim period. However, if you feel that there is a risk of them occurring, you may periodically review the balances and transfer any inappropriate charges up to the manual journal deadline immediately prior to the month-end in which your value is scheduled to be disabled.