There have been some changes to the SkyClub rules (most notably, 18 year olds can join now, but need to be 21 to be admitted to a location with a self-serve bar):
* A photo ID is required for entry into a Delta Sky Club.
* Individuals must be at least 18 years of age for Club membership. Members must be 21 years of age to access Clubs with a self-service bar.
* Attire while in a Delta Sky Club must be in keeping with good taste and a dignified atmosphere.
* Members can only use the Club in conjunction with same-day ticketed air travel but such travel may be on any airline.
* Access to partner lounges is subject to additional terms and conditions, including but not limited to the house rules of the partner lounge.
* Airline, airport, and industry employees are not permitted access while in uniform (this includes employees of other airlines, private and corporate aircraft, and charter carriers).
Third to last bullet point though still allows for access if on any airline though.