Wouldn't that be equivalent to granting a title of nobility, which the US Constitution prohibits?
Of countries that could become monarchies again- didn't Montenegro just give some official status to its royal family?
Yes they did, from the Wikipedia article on Crown Prince Nicholas II of Montenegro:
"On the 12 July 2011 the Parliament of Montenegro adopted the Law on the Status of the Descendants of the Petrović Njegoš Dynasty. [2][3]
The law "regulates the important issues regarding the status of the descendants of the Petrović-Njegoš dynasty, for the historical and moral rehabilitation of the Petrović-Njegoš dynasty for whom their dethroning was contrary to the Constitution of the Kingdom of Montenegro, a violent act of annexation in the year 1918." (Article 1).
The law recognises the descendants of King Nikola I in the male line and their wives as the descendants of the Petrović-Njegoš dynasty (Article 2), and appoints the eldest male heir, namely Prince Nikola II, as the representative of the dynasty (Article 5). It also affirms the House law of the dynasty by defining the succession to the headship of the dynasty as being passed down through the "male heir of the oldest male heir" (Article 5). The law protects the use of the heraldic symbols of the dynasty by the representative of the dynasty, Prince Nikola II (Article 6).
Article 8 allows for members of the dynasty to obtain Montenegrin citizenship and also to be dual-nationals of other nations without losing their Montenegrin citizenship. This is of particular relevance today as all of the members of the dynasty currently also hold French citizenship.
The law also creates the non-political (Article 10) Petrović-Njegoš Foundation (Article 9), an organisation chaired by Prince Nikola II (Article 10), with its aim to "affirm the Montenegrin culture and participation in humanitarian and development activities in the interest of Montenegro and its traditions" (Article 9).
From Montenegro's exchequer, the law allocates 4.3 million euros over a seven year period to the Petrović-Njegoš Foundation (Article 11). In addition, Prince Nikola II is entitled to a monthly income equivalent to the gross monthly earnings of the President of Montenegro (Article 16).
The Petrovic-Njegoš Foundation has its seat in Montenegro. "The Descendants of the dynasty are given the continuous use of the house of King Nikola I Petrović-Njegoš in Njeguši...its gardens...and meadow-land."
"Descendants of the dynasty will have built for them a family home in Cetinje...and be given an apartment in Podgorica" (Article 12).
To carry out their official functions Prince Nikola II has the right to use State objects and resources and "the exclusive right of use of the first storey" of the Petrović Palace (Dvorac Petrovića) in Podgorica, "and when protocol requires, use of the ground floor with priority over other users" (Article 13).
The law allows for Prince Nikola II to act as a representative of the Government of Montenegro and perform other protocolar and non-political functions (Article 7). The first such undertaking was made by the Prince in July 2011 when he represented the Prime Minister of Montenegro, Igor Lukšić, at the requiem of Otto von Habsburg, former Crown Prince of Austria-Hungary.
When performing functions on behalf of the Government, Prince Nikola II and the other members of the dynasty are afforded full State protocol (Article 15)."
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