In addition to the grounds for suspension in § 4–604 of this article, the Board may suspend a license for a time not exceeding 1 year for: the sale of alcoholic beverages to an individual under the age of 21 years; or the sale on Sunday of alcoholic beverages in an election district or a precinct of an election district in which Sunday sales have not been authorized by a voter referendum. The decision of the Board is conclusive.