Emerson shield rules are a reflection of Dunn shield rules, but at the same time are completely different. I too, have bowled Emerson as a substitute ( once only ) and felt guilty about taking a position that really belonged to a regular league bowler of that centre. That's why I never returned to Emerson.
There have been a number of inconsistencies at Dunn shield over the years including substitutes, number of games, cut-off dates, staff leagues, phantom leagues, rolling off for multiple centres, etc. My opinion is that substitutes ( that is, not regular paying league members ) are not eligible, they are not current league members. Otherwise a large number of people could qualify for Dunn shield at many different centres without supporting really that centre or contributing towards the leagues.
There are a number of vacancies in our league that interested parties could fill, if they intended to play Dunn shield. An increase in the size of the league ( and the prize fund ) would be greatly appreciated by the current bowlers as well as the centre management.
The question was not raised as a personal attack on any individual, rather a concern of the legality of the whole team at the time of the tournament.
However to avoid the speculation, a ruling from tournament director is the only way to obtain an accurate answer to this problem. If the rules are unclear maybe a players committee needs to be formed in future years to review the current rules and uphold rulings.