===the following comment has since be rescinded by the author, namely me. Sorry. It is wrong.===
You are quite correct. The original quote was in the wrong tense.
It would have been correct, even looking back into the past, if it said "the 1972 agreement reduces the amount they are allowed to dump" (assuming the 1927 agreement is still in force today, so it has present tense currency) - but your suggestion is the better one.
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