The phrase "hand out warning" is not correct as it is missing an article.
It should be "hand out a warning" or "hand out warnings." You can use it when referring to the act of giving someone a warning about a specific behavior or situation.
Example: "The teacher decided to hand out a warning to the students who were talking during the lecture."
Alternatives: "issue a warning" or "give a warning."
Staff at medical centres across Salford have been handing out warning leaflets on measles for days now.
The judge dotes on the jury, but is happy to hand out warnings to misbehaving reporters and aggressive lawyers.
Now the city authorities are planning a dedicated "incivility brigade" to hand out warnings and fines to persuade offenders to be better behaved.
The students perform a public service of sorts: they are encouraged to hand out warnings to cars that park illegally and chastise dog owners who do not clean up.
Not only have the Golden Dawn refused to apologise for their actions outside Corpus Christi, but the Golden Dawn MP Ilias Kasidiaris – famous for physically assaulting a leftwing politician on live TV – didn't miss the chance to hand out warnings: "In any case where the religious sentiment of Greeks is insulted, the Golden Dawn will react dynamically," he said.
The six new civil enforcement officers (CEOs) have been handing out warning notices to illegally parked vehicles since 29 May, in the run up to Monday.
She gives loud blasts on her whistle whenever she sees the thieves, who operate mostly in a dozen city centre stations including the Sagrada Familia and Placa Catalunya, and hands out flyers warning about the criminals.
And they hand out leaflets warning that an abortion can result in an "inability to become pregnant," "development of eating disorders" and "survival guilt".
So the San Mateo County Sheriff's Department set up a checkpoint and handed out warnings to errant cyclists.
Doughty has made sure to see all of Davies's recent interviews, particularly the one in Scotland, and it cannot be discounted he will sack, or hand out an official warning, to the former Derby County and Preston North End manager if he is not satisfied with the outcome of their talks.
