Triggers cannot pass parameters - you have to operate within the database operation. Therefore, unless the Cars table has a CreateBy or LastUpdateBy referencing the id of the user making the change, you would need to wrap the INSERT into a stored procedure that would perform that check before performing the INSERT.
If by chance your Cars table has a CreateBy that contains the id of the user performing the change, then a trigger such as this below should work:
CREATE TRIGGER tg_Cars_Register ON dbo.Cars
AFTER INSERT AS
BEGIN
IF EXISTS (SELECT * FROM INSERTED WHERE CreateBy <> 1110) BEGIN
RAISERROR('Unauthorized parking', 16, 1)
ROLLBACK
RETURN
END
END
GO