David Beckham's Inter Miami violated Major League Soccer roster and salary rules over the signing of French international Blaise Matuidi, the league confirmed in a statement on Friday.
MLS said the 34-year-old French World Cup-winner had been paid more than allowed under the league's roster and budget rules, effectively giving Miami four "designated players" last season rather than the allowed three.
Each team in MLS is allowed three designated players, whose wages do not count against the salary cap.
The rule is sometimes called the "Beckham Rule" as it was introduced when it was adopted shortly before the former England and Manchester United star joined the league in 2007.
An MLS statement said an investigation into Matuidi's transfer found the Frenchman had been wrongly categorised as a "targeted allocation money (TAM)" player.
"Matuidi's compensation was above the compensation limit for a TAM player and he should have been classified as a designated player," the statement read.
"As a result, Inter Miami CF violated the designated player limit as the team had three designated players in addition to Matuidi during 2020."
The league said it is finalising its investigation and will announce findings and sanctions in the near future.
In order to make their 2021 roster compliant, Miami have been forced to buy out the contract of one of their other designated players, Argentine midfielder Matias Pellegrini.
Pellegrini has now signed for Fort Lauderdale CF -- Miami's offshoot in the lower tier United Soccer League League One -- and will not be eligible to play in MLS this season.
Matuidi is now one of Miami's designated players alongside Argentine striker Gonzalo Higuain and Rodolfo Pizarro.