1.3 adds a lock gate to the planet govern button in the PlanetGovernLockTech .  If you set that to TechTree (which everyone gets), it stays locked.  You have to instead set it to something like one of the tier1 techs (ie TranslatorTech) and research that to open the gateway.  also because of the location/format it can't be gated with multiple options like you can wiith techs

<Prerequ>
<Techs>
<Option>IndustrialSpecialization1</Option>
<Option>IndustrialSpecialization2</Option>
<Option>IndustrialSpecialization3</Option>
</Techs>
<TechAge>
<Option>AgeOfExpansion</Option>
</TechAge>
</Prerequ>

it feels like maybe it should go in GovernorBonusDefs.xml where any mod affecting it is likely to live