Terminals in Ukraine are whitelisted (with whitelist being supplied by the Ukrainian MoD). Meaningful controls are possible, it's what led to the ukrainian forces advancing and liberating territory recently.
And while geofencing + allow-listing for sure provide value in e.g the Ukrainian conflict, it's a weak protection compared to goods that are actually under strict export control (e.g ITAR), and will always have to be done after the fact. Russia could for example put Starlink on drones launched from the Baltic Ocean targeting Poland or whatever.