My son was stopped by the police and was told he had a 'Drugs marker' against his name and they searched him. Does this mean he won't be able to apply for an ESTA to go on holiday to America next year?
Put simply, it is a flag up of suspicion against a person and/or vehicle when details are run through the system - indicating that in the past there has been some connection with drugs.
I'd guess if the police stopped someone with with this against his name and radioed for information they'd be told that he had a place in the drug world.