This has been pulled from the USMS.org site. Please check their site for the latest rules regarding competition legal swim suits.
pursuant to Article 601.4.8, the USMS Rules Committee and the USMS Executive
Committee have approved the following emergency changes to the USMS swimwear
rules. These changes are effective immediately for short course meters and long course
meters competition. The changes are effective June 1, 2010 for short course yards
competition. Note that the new swimwear rules no longer allow modesty/privacy wear
underneath the competition suit nor zippers or fasteners of any kind except for a waist tie
on a brief or jammer. The new swimwear rules will not govern the One Hour Swim
being conducted January 2010.
Changes to the swimwear rules are underlined below.
102.14.1 Design-The swimsuits worn for competition shall be nontransparent and conform to the current concept of the appropriate. The referee shall have authority to bar offenders from competition until they comply with this rule.
102.14.3 In swimming competitions, the competitor must wear only one swimsuit in one or two pieces. All swimsuits shall be made from textile materials. Except for open water competitions, for men, the swimsuit shall not extend above the navel nor below the knees, and for women, shall not cover the neck, extend past the shoulder, nor extend below the knees.
102.14.4 Only swimsuits complying with FINA swimsuit specifications may be worn in any U.S. Masters Swimming sanctioned or recognized competition.
102.14.5 Exemptions to the foregoing restrictions may be granted to a swimmer, on a case by case basis, by the Chair of the Rules Committee or designee. Exemptions will be granted only for conflicts due to the swimmer's verified religious beliefs or verified medical conditions.
102.14.6 Swimmers are not permitted to wear or use any device or substance or swimsuit to help their speed, pace, buoyancy or endurance during a race (such as webbed gloves, flippers, fins, etc.). Goggles may be worn, and rubdown oil applied if not considered excessive by the Referee. Any kind of tape on the body is not permitted unless approved by the Referee.
102.14.7 Advertising-Products involving tobacco, alcohol or pharmaceuticals containing drugs banned under IOC or FINA rules may not be advertised, but the advertiser's name only may be used. Offenders may be barred from competition until they comply with this rule.
Kathy Casey, Chair
USMS Rules Committee
You may also view the Emergency Rule Change at usms.org.