What’s the difference between these two examples?

1. Does a conflict of interest exist where attorneys, who are married to each other, represent opposing parties in the same civil matter?

1a. Does a conflict of interest exist where attorneys who are married to each other represent opposing parties in the same civil matter?

In number 1, the clause “who are married to each other” is a nonrestrictive clause because it’s set off with commas. So that clause, or modifier, doesn’t restrict the attorneys involved; rather, it purports to give us information about attorneys. But that doesn’t make sense. Attorneys are married to each other? All attorneys?

In 1a, the clause “who are married to each other” is a restrictive clause because it’s not set off with commas. So that clause restricts the attorneys involved to those who are married to each other, which makes sense.

One more pair:

2. The lawnmower, which is broken, is in the garage.

2a. The lawnmower that is broken is in the garage.

Now we have relative pronouns in addition to the presence or absence of commas to help us.

In number 2, the clause “which is broken” is a nonrestrictive clause because it’s set off with commas. So that clause doesn’t restrict the lawnmower involved; rather, it gives us information about the lawnmower–it is broken. That makes sense, but it’s a different meaning from 2a.

In 2a, the clause “that is broken” is a restrictive clause because it’s not set off with commas. So that clause restricts the lawnmower involved to the one that is broken. By the way, the implication of 2a is that there’s more than one lawnmower around, so the writer/speaker is specifying the one that is broken.

The commas in number 1 are technically incorrect, but the mistake probably isn’t fatal. Most readers would understand that the question refers to attorneys who are married to each other.