Which is correct? in commission of federal crime(s) by his longtime lawyer.
Which is correct? in commission of federal crime(s) by his longtime lawyer.
in the commission of federal crime(s) by his longtime lawyer.

Most important, the plea states that Cohen, in committing the campaign-finance violations, acted at the behest of the “candidate.” There is only one candidate. The president of the United States has now been implicated in commission of federal crime(s) by his longtime lawyer.

Question

Which is correct? in commission of federal crime(s) by his longtime lawyer.
Which is correct? in commission of federal crime(s) by his longtime lawyer.
                               in the commission of federal crime(s) by his longtime lawyer.

Most important, the plea states that Cohen, in committing the campaign-finance violations, acted at the behest of the “candidate.” There is only one candidate. The president of the United States has now been implicated in commission of federal crime(s) by his longtime lawyer.

Answer

It’s probably debatable. ‘Commission’ without the definite article might seem ambiguous, but the sentence here makes the meaning clear. To my mind I would add ‘the’ before commission, but that would also read more as a direct assertion that ‘the candidate’ has committed crimes.