T SQL CHECK Constraint to allow uppercase set of values

I have to create a table in SQL Server using a check constraint to allow only Uppercase set of values

My code as this:

CREATE TABLE Client(
    clientID INT IDENTITY(1,1) PRIMARY KEY,
    FirstName VARCHAR(30) NOT NULL,
    LastName VARCHAR(30) NOT NULL,
    StreetAddress VARCHAR(50),
    Suburb VARCHAR(25),
    State VARCHAR(4) CHECK (state in ('QLD', 'NSW', 'VIC', 'TAS', 'SA', 'WA', 'NT', 'ACT')),
    PhoneNumber VARCHAR(10)
);

Please check the Error and help me