Major League Baseball has issued a warning to clubs about trying to encourage high school players to withdraw from their school's baseball team, thus making them eligible to sign as international free agents.

ESPN's Kiley McDaniel obtained a copy of the memo that was sent out to teams on Monday:

"It has come to our attention that Clubs have been encouraging amateur players in the United States to withdraw from, or otherwise refrain from playing, high school baseball in the United States and/or Canada, in order to try to establish residency in a foreign country, in an effort to make themselves eligible to sign under the International Amateur Talent System instead of the Rule 4 Draft."

According to the memo, teams were warned they would be "subject to significant penalties, including, but not limited to, the denial of player selection rights under the [MLB draft] or loss of benefits under the International Amateur Talent System" if they encouraged players to change their eligibility.

International free agency allows for all 30 teams to potentially sign a player, as opposed to the draft where the top prospects are typically relegated to the clubs based on their draft slot.

Per MLB's official rules, players residing outside of the United States, Canada or Puerto Rico and not enrolled in high school in any of those locations within the past calendar year are classified as international amateurs.

International amateur status also qualifies for players who are at least 16 years old or who will turn 16 prior to Sept. 1 of the current signing period.

McDaniel cited the situation with Lucius Fox in 2015 as a recent example of a player taking advantage of the international free-agent rules.

Fox was originally born in the Bahamas before moving to Florida at the age of 12. He moved back to the Bahamas in 2015 and MLB approved his petition to become an international free agent.

The San Francisco Giants wound up giving Fox a then-franchise record $6 million bonus in July 2015.

For perspective, the only player in the 2015 draft who received a bigger signing bonus than Fox's deal with the Giants was No. 1 overall pick Dansby Swanson from the Arizona Diamondbacks ($6.5 million).

MLB didn't have a hard cap on international signing bonus money at the time Fox signed his deal. That was implemented in 2016, so a player who went the Fox route now almost certainly wouldn't get as much money if they signed today.

The league has tried to push for an international draft for years, but the MLB Players Association has consistently rejected the proposal.