Yes, the verb "helfen" requires that its object be in the dative case.
You can also use a preposition like "gegen" oder "bei" with the verb "helfen", as in
Aspirin hilft gegen/bei Kopfschmerzen.
In this case the case is determined by the preposition, as with every other verb.
Moreover, "helfen" can be accompanied by an infinitve, as in
Er half aufräumen.
However, if "helfen" is used with an object, it has to be in the dative case.
That said, the sentence fragment you provided doesn't necessarily have to be wrong. If you have a sentence like
Um bei der Durchsetzung von Schutzmaßnahmen für die Umwelt zu helfen [..]"
"die Umwelt" is actually the object of the preposition "für", which requires the accusative case.