The European Commission, which oversees competition policy in the 27-member European Union, said it had opened the study after two rival gaming operators complained in March 2019 that Ladbrokes' exclusive right amounted to unfair state aid.
Ladbrokes is operated in Belgium by Derby SA, a subsidiary of GVC Holding PLC, and is the market leader with some 300 betting agencies in the country.
The Commission said Belgium authorised Ladbrokes to operate virtual betting in its outlets in February 2014 and online in March 2015, but then denied requests from other operators.
"The measure may have distorted competition and the Commission has doubts that it complies with EU state aid rules," the Commission said in a statement.
(Reporting by Philip Blenkinsop; editing by Marine Strauss and Jason Neely)