When something is said to be of the king's, it means that it is of high quality or importance. The king is the head of the monarchy, and his rule is considered to be very important.
The dress is said to be of the king's, because it is very luxurious and stylish.
The king's rule is said to be good for the people, because he is responsible for ensuring that the country is safe and stable.
noun
the dignity or rank or position of a king
1
The institution of kingship was general.
2
She was the heavenly regent of the kingship.
3
In April 1192, the kingship was put to the vote.
4
Dhatusena claimed the kingship of the country in 455.
5
The Germans upheld his claim for the kingship.
6
He took the kingship of Dublin in the year 1075.
7
The sacred king combines the offices of kingship and priesthood.
8
In her human guise, she was the heavenly regent of the kingship.
9
He succeeded Husham in the apparently elective kingship of the Edomites.
10
The dual kingship diluted the effective power of the executive office.