Trouble writing table constraint

ALTER TABLE addresses
ADD CHECK (
CASE
	WHEN country=1 THEN state IS NULL AND zipcode IS NULL
	WHEN country=2 THEN province IS NULL AND postalcode IS NULL
	ELSE true
END
)

create table addresses
(
    addressID SERIAL8 NOT NULL PRIMARY KEY,
    address VARCHAR(255) NOT NULL,
    city VARCHAR(64) NOT NULL,
    state INT2 REFERENCES states(stateID) ON UPDATE CASCADE,
    canProv INT2 REFERENCES provinces(provID) ON UPDATE CASCADE,
    provName VARCHAR(64),
    zip CHAR(10),
    canZip CHAR(7),
    postalCode VARCHAR(12),
    country INT2 NOT NULL REFERENCES countries(countryID) ON UPDATE CASCADE,
    CONSTRAINT checkAddress
        CHECK
        (
            CASE
                WHEN country=1 
                    THEN state IS NOT NULL 
                    AND zip IS NOT NULL 
                    AND zip ~ '^[0-9]{5}(-[0-9]{4})?$' 
                    AND canProv IS NULL 
                    AND canZip IS NULL
                    AND provName IS NULL
                    AND postalCode IS NULL
                WHEN country=2 
                    THEN canProv IS NOT NULL 
                    AND canZip IS NOT NULL 
                    AND canZip ~ '^[A-Z][0-9][A-Z] [0-9][A-Z][0-9]$'
                    AND zip IS NULL
                    AND state IS NULL
                    AND provName IS NULL
                    AND postalCode IS NULL
                WHEN country>2 
                    THEN state IS NULL
                    AND zip IS NULL
                    AND canProv IS NULL
                    AND canZip IS NULL
                ELSE FALSE
            END
        )
)