If this policy is not set, the user can enable or disable spellcheck in the language settings.
If this policy is set to true, spellcheck is enabled and the user cannot disable it. On Microsoft® Windows, Google Chrome OS and Linux, spellcheck languages can be individually toggled on or off, so the user can still effectively disable spellcheck by toggling off every spellcheck language. To avoid that, the SpellcheckLanguage policy can be used to force specific spellcheck languages to be enabled.
If this policy is set to false, spellcheck is disabled and the user cannot enable it. The SpellcheckLanguage and SpellcheckLanguageBlacklist policies have no effect when this policy is set to false.