[DannyTN]

"Declaratory judgments are authorized by statute in most common-law jurisdictions. In the United States, the federal government and most states enacted statutes in the 1920s and 1930s authorizing their courts to issue declaratory judgments.[7]"

Wikipedia Declaratory Judgements

[Hawthorn]

>> the federal government and most states enacted statutes in the 1920s and 1930s authorizing their courts to issue declaratory judgments <<

I scanned the Wikipedia article you cited, and all I could find was that Federal courts are authorized by statute to issue declaratory judgments only in patent and other intellectual property cases. So unless I missed some detail that you’ve found, there would seem to be no chance of their issuing a declaratory judgment about Cruz’s citizenship.