This is the first movie he had a starring role in since 2003 - he has been in plenty of supporting roles. For one thing it makes me a bit sad to see one of my childhood heroes get older, but that being said; for fans of Schwarzenegger's style, this movie is entertaining enough.
Arnold is of course a law-enforcement officer, who has taken a post in a town where very little in the way of crime ever happens. There are very few people that even live in this sleepy border town in Arizona and as you would expect, Arnold has a sort of special forces past that enables him to handle much bigger situations than parking tickets.
The towns truly eccentric resident is named Lewis Dinkum (played by Johnny Knoxville) and he just happens to be the collector or a large cache of weapons
This ends up being extremely convenient when a group of drug lords decide to use their town as an escape route for a crime boss who recently broke out of FBI custody in a suped up Corvette which is likely in the movie as some sort of expensive advertising for Chevrolet.
As is usual with Arnold films, the odds are stacked firmly against him since backup can not possibly make it in time to help out and it is up to him, his 2 deputies, and Dinkum to stop this escape.
If the things i mentioned above seem like spoilers I think it could only be perceived as such by someone that has never seen a Schwarzenegger film and I don't think there are any of those people who are over 10 years old. The movie is extremely predictable, but filled with good effects and fun action. However, this is not a movie i would recommend anyone go terribly out of their way to see. It is good, mindless entertainment.