Tautology or not?

Hi.

I’d be grateful for your help for what, on first glance may appear to be a legal question, but I believe that its essence is an English question.

I was recently involved in a court case where a contract used the phrase "deal must be effected by themselves". The phrase referred to the conditions under which someone would be entitled to a commission.

The judge said that if the clause had said "must be effected by themselves ONLY", it could be accepted that the contracted person had to effect a deal on their own and without the assistance of anyone else to receive a commission, but that without the word “only”, it would refer to any deal done by the person, irrespective of if they did the deal on their own or not.

It has since been contended that the judge's preferred statement represents tautology in English. Does the phrase mean “on their own and without the assistance of anyone else” without the added “only”?

What do you think?

Craig.