Partciluarly, is it permissible to enforce a law like punishing someone for speeding on the highway? What about allowing someone to drink alcohol if he is over 21 but not if he is under 21? Even though this is not Islamic, should a Muslim allow such behaviour among non-Muslims? Of course, Muslims will be accountable for these haraam actions in the Hereafter, but is it okay to let non-Muslims do this?
Praise be to Allah.
If a Muslim is able, through such work, to fight evil and oppression, or to prevent or reduce it by using the existing laws which may contain something of justice and decency, then it is permissible if his intention is to seek the pleasure of Allah. He may do this work even if it involves preventing only some people - but not all - from getting drunk, for example.
But if it involves enforcing laws that are unjust to people - whether they are Muslim or not - or enforcing something that goes against the Sharee'ah, like preventing people from wearing hijaab or praying, or giving some kind of protection to criminals, and so on, then this is not permitted at all.
The wise and clever Muslim knows from experience to what extent his work is in accordance with the Sharee'ah that is based on the common good and on preventing corruption. And Allaah knows best.
Sheikh Muhammed Salih Al-Munajjid