"Persons travelling abroad as designated officials with ECF teams which include junior players" absolutely need DBS - no argument.
"Arbiters who perform their duties at junior congresses" would not be eligible for DBS for that particular role since the level of unsupervised contact with children is below the threshold where DBS can be legally demanded. Individuals who are Arbiters may have previously obtained DBS for a different role (eg. as a professional teacher, after school club superviser and similar) but it cannot be demanded simply for being an Arbiter at Junior events and should be removed from the list.
Although individuals or organisations might think that they should demand DBS "just to be sure", the ECF Safeguarding document should make it clear that, in fact, it is illegal to demand DBS for a role which does not meet the DBS eligibility criteria.
[1] ECF Safeguarding Policy: http://www.englishchess.org.uk/safeguar ... en-policy/About DBS[2] wrote: DBS check eligibility
Access to the DBS checking service is only available to registered employers who are entitled by law to ask an individual to reveal their full criminal history (other than protected cautions and convictions), including spent convictions - also known as asking ‘an exempted question’.
[2] About DBS: https://www.gov.uk/government/organisat ... vice/about
[3] DBS Home page: https://www.gov.uk/government/organisat ... ng-service