2018 FIFA World Cup. Major League Soccer in the United States introduced VAR in competitive matches during its 2017 season after the 2017 MLS All-Star Game on 2 August 2017. Gridiron football codes In American and Canadian football, instant replay can take place in the event of a close or otherwise controversial call, either at the request of a team's head coach (with limitations) or the officials themselves. There are restrictions on what types of plays can be reviewed. In general, most penalty calls or lack thereof cannot be reviewed, nor can a play that is whistled dead by the officials before the play could come to its rightful end. American and Canadian football leagues vary in their application and use of instant replay review. In the National Football League, each coach is allowed two opportunities per game to make a coach's challenge, and get a third challenge if both of the original two challenges were successful. A challenge can only be made on certain reviewable calls on plays that begin before the two-minute warning and only when a team has at least one timeout remaining in the half. The Canadian Football League uses similar rules as the NFL, except the game has a three-minute warning near the end of each half instead of two. In NCAA football, each team only has one challenge per game, and gets a second challenge if the first one is successful. In all three rules codes, the challenging team is charged with a timeout if their challenge is unsuccessful. U.S. high school rules prohibited the use of replay review, even if the venue had equipment that allows the practice, before 2019, when the National Federation of State High School Associations (NFHS) gave its member associations the option to allow its use in postseason games only. In Texas, where high schools have always based their rules on those of the NCAA, the University Interscholastic League, which governs public-school sports, allows its use only in state championship finals. The main governing body for Texas private schools, the Texas Association of Private and Parochial Schools, follows pre-2019 NFHS practice by banning replay review. Field hockey In field hockey, the International Hockey Federation allows the match umpire to request the opinion of a video umpire as to whether or not a goal has been validly scored, and whether there was a violation in the build-up to a goal.