Although it has not been officially announced (that I have noticed anywhere), it appears as though the Frontier League has tweaked their roster rules, including increasing the age to 28 (from 27), and adding four veteran roster spots for players over the age of 28. The minimum number of rookies also went down from twelve to ten.
Most of the basic rules, including exemptions and rule regarding pay-to-play leagues have remained the same.
The complete list of player eligibility per the Frontier League website can be found below:
During the off-season, teams may have no more than thirty-four (34) players on their active roster. There is no classification limit for the off-season roster. Players signed out of the California Winter League or selected in the Frontier League Draft are exempt from the 34-player limit.
The Sunday prior to Opening Day (May 10 for the 2020 season), teams must be down to 28 players.
Regular season and playoff club rosters will be composed of a minimum of 22 active players and a maximum of 24 active players.
Each club must carry a minimum of ten (10) rookies (combination of Rookie-1 and Rookie-2 players) with no professional experience other than specified below and may carry a maximum of ten (10) players classified as Experienced-2 or Veteran during the regular season and playoffs on their active roster.
No player or player/coach may have attained twenty-eight (28) years of age prior to October 1 of that playing season with the exception of the four Veteran classification players as described below.
Players without prior affiliated baseball (MiLB) experience must be at least 18 years old to play in the Frontier League.
Rookie Classification: The Rookie classification will be split into two sub-classifications, Rookie-1 and Rookie-2. The Rookie-1 sub-classification will be for players who made their professional debut in the current season and therefore have no prior professional experience, or whose experience does not meet the minimum appearances listed below. The Rookie-2 sub-classification is for players who have one year of professional experience.
Experienced-1 Classification: The Experienced-1 classification is for players who held, or would have held if they played in the Frontier League, the Rookie-2 classification in the previous season, subject to the minimum appearances described below.
Experienced-2 Classification: The Experienced-2 classification is for all players who do not meet the requirements to be classified under the Rookie, Experienced-1, or Veteran classifications.
Veteran Classification: The Veteran classification is for a player who is over twenty-eight (28) years of age prior to October 1 of that playing season.
Minimum Appearance Exception: A player must have accrued more than 75 at bats, 15 games pitched, or 30 innings pitched in a season for that season to count toward the classifications.
21-year Old Exemption: Any player who is twenty-one (21) years of age or younger on or after October 1st of any season and is entering his first year in the Frontier League, regardless of any prior professional baseball experience, will be considered no higher than a Rookie-2 by Frontier League Rules. For the 2020 season, a birthdate of October 1, 1998 will be the cutoff to qualify under this provision.
Military Exemption: Players who have served on active military duty will receive an exemption to the age limit of one year for each year of active duty that was served.
Position Change Exemption: Starting with the 2016 season, position players who are switching to pitching and pitchers who are switching to playing a position will have their classifications reset to Rookie-2 provided that they do not appear in any games at their previous position (batting/running or pitching, depending on the switch).
The California Winter League is the exclusive winter league of the Frontier League.
The Frontier League is proud to have extended our agreement with the California Winter League and to make the California Winter League the Exclusive Winter/Showcase League of the Frontier League.
Players who participate after May 1, 2018 in a pay-to-play league or a league that charges a fee to attend their spring training will be ineligible for the Frontier League unless the player has had contact with the Frontier League.
Contact with the Frontier League includes:
Having ever been under contract to a Frontier League team;
Having participated in a past Frontier League Tryout Camp and Draft;
Participating in the 2019 Frontier League Tryout Camp and Draft (for the 2019 Frontier League season)
Having participated in a past California Winter League season; or
Participating in the 2019 California Winter League season (for the 2019 Frontier League season)
Leagues that are covered by this provision are:
Arizona Winter League/Pro Prospect Winter Leagues, LLC
South Florida Winter League / Baseball Scouting League
Hudson River League
Puerto Rican Instructional Baseball League
Please note that this provision is not retroactive and only applies to players participating on one of these leagues after May 1, 2018.