A gerund or a gerund phrase is always singular as a subject

Is the following statement grammatically correct? “Please wear your proper uniform. Wearing of shorts, sandos, and slippers are strictly prohibited.”

That question was posted recently in Jose Carillo’s English Forum by a member who goes by the username Youssef. When he joined the Forum in January of 2012, Youssef described himself then as a “non-traditional” college student almost in his mid-thirties, and I recall receiving two private notes from him expressing appreciation for the Forum’s insights and tips that he said were helping broaden his English skills.