Here are the referee assignments for all the MLS matches in Week 12, per Professional Referees Organization (PRO).
SATURDAY, MAY 18
Toronto FC vs. Columbus Crew
    BMO Field (5:00 pm ET)
    REFEREE: JOSE CARLOS RIVERO
    ASST 1: Chris Strickland
    ASST 2: Marco Arruda
    4TH: Hilario Grajeda
Vancouver Whitecaps vs. Portland Timbers
    BC Place (7:00 pm ET)
    REFEREE: MATTHEW FOERSTER
    ASST 1: Jeff Hosking
    ASST 2: Eric Proctor
    4TH: Drew Fischer
Philadelphia Union vs. Chicago Fire
    PPL Park (7:30 pm ET)
    REFEREE: DAVE GANTAR
    ASST 1: Eric Boria
    ASST 2: Kevin Klinger
    4TH: Kevin Terry Jr
Houston Dynamo vs. New England Revolution
    BBVA Compass Stadium (8:30 pm ET)
    REFEREE: EDVIN JURISEVIC
    ASST 1: George Gansner
    ASST 2: Frank Anderson
    4TH: Armando Villarreal
San Jose Earthquakes vs. Colorado Rapids
    Buck Shaw Stadium (10:30 pm ET)
    REFEREE: RICARDO SALAZAR
    ASST 1: Ian Anderson
    ASST 2: Colin Arblaster
    4TH: Allen Chapman
Seattle Sounders vs. FC Dallas
    CenturyLink Field (10:30 pm ET)
    REFEREE: MARK GEIGER
    ASST 1: Joe Fletcher
    ASST 2: Claudio Badea
    4TH: Baldomero Toledo
SUNDAY, MAY 18
New York Red Bulls vs. Los Angeles Galaxy
    Red Bull Arena (1:00 pm ET)
    REFEREE: SILVIU PETRESCU
    ASST 1: Peter Manikowski
    ASST 2: Gregory Barkey
    4TH: Jorge Gonzalez
D.C. United vs. Sporting Kansas City
    RFK Stadium (5:00 pm ET)
    REFEREE: JAIR MARRUFO
    ASST 1: Paul Scott
    ASST 2: Matthew Nelson
    4TH: Daniel Fitzgerald
Chivas USA vs. Real Salt Lake
    The Home Depot Center (10:30 pm ET)
    REFEREE: SORIN STOICA
    ASST 1: Corey E Rockwell
    ASST 2: Fabio Tovar
    4TH: Juan Guzman

 
              


