[css3-conditional] @supports compounds with general_enclosed

Hello,

I was reading the section on @supports and the general_enclosed production. [1] The general_enclosed production is “always false. Additionally, style sheets must not write ‘@supports’ rules that match this grammar production.” What does the “must not write” portion entail? Can the general_enclosed production still be part of an overall true production, if combined using a disjunction and a true condition, or negated? I ask because some implementations maintain the general_production in CSSConditionalRule’s conditionText and cssText [2] for a production like "@supports((margin: 0) or (green))”, and I wasn’t sure if this counted as writing or not.

Thanks for your help,
-Bear Travis

[1] http://www.w3.org/TR/css3-conditional/#at-supports

[2] http://www.w3.org/TR/css3-conditional/#cssconditionrule